Hardy started on World Wrestling Federation (WWF) television as a jobber. His first WWF match was against Razor Ramon on May 23, 1994 in Youngstown, Ohio. The next day, he wrestled against The 1-2-3 Kid, and the match aired on the June 25 episode of Superstars. He occasionally wrestled as a jobber as late as 1997 (including a match against Rob Van Dam during the ECW "invasion" storyline that had Hardy billed as being from Virginia instead of Cameron, North Carolina).
Jeff, along with his brother Matt, eventually caught the eyes of the World Wrestling Federation (WWF). They were officially signed to a contract in 1998. When the team was finally brought up to WWF television, after months of "jobbing" and live events, they formed the acrobatic tag team called the Hardy Boyz. While feuding with The Brood in mid-1999, they added Michael Hayes as their manager. On July 5, they won their first WWF Tag Team Championship by defeating the Acolytes, but lost it back to them a month later. After the dissolution of the Brood, the Hardys joined forces with Gangrel as The New Brood and feuded with Edge and Christian. This stable did not last long, however, and on October 17, 1999 at No Mercy, the Hardy Boyz won the managerial services of Terri Runnels in the finals of the Terri Invitational Tournament in the WWF's first ever tag team ladder match against Edge and Christian. They competed in the first ever tag team triple threat ladder match against The Dudley Boyz, and Edge & Christian at WrestleMania 2000, in which Edge & Christian won. During the match, Hardy performed a Swanton Bomb to Bubba Ray Dudley off a 20-foot ladder. They also competed in the first two TLC (Tables, Ladders and Chairs) matches ever, both against Edge and Christian and The Dudley Boyz.
In 2000, the Hardy Boyz found a new manager in Lita. Together, the three became known as "Team Xtreme". They continued their feud with Edge and Christian throughout 2000, defeating them for the WWF Tag Team Championship on two occasions. At SummerSlam, the Hardy Boyz competed in the first ever Tables, Ladders, and Chairs match (TLC match) in their hometown of Raleigh, for the Tag Team Championship against the Dudley Boyz and Edge & Christian, but were unsuccessful.
Hardy gained attention for his high risk stunts in the TLC matches, making a name for himself as one of the most seemingly reckless and unorthodox WWF performers of his time. In 2001, Hardy received a push as a singles competitor, and he held the Intercontinental (defeating Triple H), Light Heavyweight (defeating Jerry Lynn) and Hardcore Championships (defeating Mike Awesome and Van Dam on two separate occasions). At the end of 2001, the Hardys began a storyline in which they began to fight, which led to Matt demanding a match at Vengeance, with Lita as the special guest referee. After Hardy beat Matt by pinfall at Vengeance, while Matt's foot was on the ropes, Hardy and Lita began feuding against Matt. In the middle of the feud, however, Hardy faced The Undertaker in a Hardcore Championship match and lost. After the match, The Undertaker was scripted to attack both Hardy and Lita, injuring them. On the next episode of SmackDown!, The Undertaker attacked Matt as well, also injuring him, in storyline. The Hardys and Lita were not seen again until the Royal Rumble, because WWF did not have another storyline for their characters. The Hardys later came back as a team, and there was never any mention of their previous storyline split.
In early April 2002, the Hardy Boyz began a feud with Brock Lesnar after Lesnar gave Matt an F-5 on the steel entrance ramp, which led to an angered Hardy seeking revenge on Lesnar. At Backlash, Hardy faced-off against Lesnar in Lesnar's first televised match. Lesnar dominated Hardy and won the match by knockout. Lesnar and the Hardys continued to feud over the next few weeks, with the Hardys coming out victorious only once by disqualification. At Judgment Day, Lesnar gained the upper hand on the Hardy Boyz before tagging his partner, Paul Heyman, in to claim the win for the team. In July 2002, Hardy won his third Hardcore Championship by defeating Bradshaw.
After years in the tag team division, Hardy took on The Undertaker in a ladder match for the WWE Undisputed Championship. Hardy came up short in the intense match, but earned The Undertaker's respect when he displayed courage by attempting to rise to his feet after the bout and challenge The Undertaker to continue. Hardy competed for singles titles on several occasions and defeated William Regal for the European Championship. Hardy was defeated a few weeks later by Rob Van Dam in a ladder match to unify the European Championship and the Intercontinental Championship, and the European Championship was retired. Finally, the Hardy Boyz split apart, as Hardy continued to pursue his singles ambitions on Raw and his brother, Matt left Raw for his own singles pursuits signing with Stephanie McMahon's SmackDown! brand. On Raw, Hardy would compete in WWE's Hardcore division until the title's unification with the Intercontinental Championship.
In late 2002, Hardy had been teaming with Rob Van Dam and Bubba Ray Dudley. He, along with Bubba Ray and Spike Dudley, defeated 3-Minute Warning at Survivor Series in a six-man tag team elimination tables match.
In January 2003, Hardy briefly turned into a heel (villain) after he attacked Van Dam and Shawn Michaels. It ended a month later when he saved Stacy Keibler from an attack by then-villain, Christian. In February, he had a brief program with Michaels, which saw the two team up. Then, in storyline, Hardy began dating Trish Stratus after saving her from Steven Richards and Victoria in March. Hardy and Stratus had a brief on-screen relationship that saw the duo talking backstage and teaming together in matches. Hardy competed in his final match (his first departure) against The Rock and lost. Hardy was released from WWE on April 22, 2003.
On August 4, 2006, WWE announced that Hardy had re-signed with the company. In the following weeks, vignettes aired hyping his return on the August 21 episode of Raw. On the day of his return, Hardy received a push and defeated then-WWE Champion Edge by disqualification when Lita pulled Edge out of the ring. After failing to capture the Intercontinental Championship from Johnny Nitro over the next few weeks, including at Unforgiven, Hardy finally defeated Nitro to win his second Intercontinental Championship on the October 2 episode of Raw. On the November 6 episode of Raw, Hardy lost the Intercontinental Championship back to Nitro, after Nitro hit him with the Intercontinental Championship title belt. One week later, Hardy regained it on the November 13 episode of Raw, with a crucifix pin. This marked Hardy's third reign as Intercontinental Champion.
On the November 21 episode of ECW on Sci Fi, Hardy teamed with his brother, Matt, for the first time in almost five years to defeat The Full Blooded Italians. At Survivor Series, they both were a part of Team D-Generation X, which gained the victory over Team Rated-RKO with a clean sweep. The brothers then received their first opportunity since Hardy's return to win a tag team championship at Armageddon. They competed in a four-team ladder match for the WWE Tag Team Championship, but they came up short in their attempt. In the course of the match, however, they inadvertently legitimately injured Joey Mercury's face.
With Hardy still feuding with Johnny Nitro and the other members of MNM into 2007, he was challenged once again by Nitro at New Year's Revolution in a steel cage match for the Intercontinental Championship. Hardy once again defeated Nitro. Hardy then teamed with Matt to defeat MNM at both the Royal Rumble and No Way Out pay-per-views. The next night on Raw, February 19, Hardy lost the Intercontinental Championship to Umaga. In April 2007, Hardy competed in the Money in the Bank ladder match at WrestleMania 23. During the match, Matt threw Edge onto a ladder and encouraged Hardy, who was close to the winning briefcase, to finish him off. Hardy then leaped off the 20-foot-high (6.1 m) ladder, drove Edge through the ladder with a leg drop, seemingly injuring both Edge and himself. The two were unable to continue the match and were removed from ringside on stretchers.
The night after WrestleMania on Raw, April 2, the Hardys competed in a 10-team battle royal for the World Tag Team Championship. They won the titles from then WWE Champion John Cena and Shawn Michaels by last eliminating Lance Cade and Trevor Murdoch. They then began a feud with Cade and Murdoch, with the Hardys retaining the Championship in their first title defense against them at Backlash and again at Judgment Day. The Hardys then defended their titles against The World's Greatest Tag Team in a Ladder match at One Night Stand. However, the next night on Raw, the Hardys lost the titles to Cade and Murdoch, competing through injuries sustained in their previous night's ladder match. The Hardys earned a rematch at Vengeance: Night of Champions but were defeated.
In the midst of feuding with Umaga, who defeated Hardy at The Great American Bash to retain the Intercontinental Championship in late July, Hardy was abruptly taken off WWE programming. He made his return on the August 27 episode of Raw, defeating Mr. Kennedy by disqualification after Umaga interfered. The following week, on September 3, Hardy successfully captured his fourth Intercontinental Championship by defeating Umaga.
This was the start of a push for Hardy, and at Survivor Series, Hardy and Triple H were the last two men remaining to win the traditional elimination match. Hardy began an on and off tag team with Triple H, which eventually led to a respectful feud between the two. The rivalry continued at Armageddon, when Hardy defeated Triple H to become the number one contender for the WWE Championship. In the weeks leading up to the Royal Rumble, Hardy and Randy Orton engaged in a personal feud, which began when Orton kicked Hardy's brother, Matt, in the head in the storyline. Hardy, in retaliation, performed a Swanton Bomb on Orton from the top of the Raw set and seemed to have all the momentum after coming out on top in their encounters. Hardy, however, lost the title match at the Royal Rumble, but was named as one of six men to compete in an Elimination Chamber match at No Way Out, where he survived to the final two before being eliminated by the eventual winner, Triple H.
During the March 3 episode of Raw, Hardy appeared on Chris Jericho's Highlight Reel segment as a special guest, but ended up attacking Jericho. This led to an Intercontinental title match on the following Raw where Hardy dropped the title to Jericho. Off-screen, Hardy dropped the title after he was suspended for sixty days, as of March 11, for his second violation of the company's Substance Abuse and Drug Testing Policy. Hardy was also removed from the Money in the Bank ladder match at WrestleMania XXIV in which he was booked to win after the suspension was announced. Hardy returned on the May 12 episode of Raw, defeating Umaga. This reignited the rivalry between the two, and they met in a Falls Count Anywhere match at One Night Stand, which Hardy won.
On June 23, 2008, Hardy was drafted from the Raw brand to the SmackDown brand, as a part of the 2008 WWE draft. Hardy made his SmackDown debut on the July 4 episode, defeating John Morrison. Hardy participated in the WWE Championship Scramble match at Unforgiven and also challenged for the championship at No Mercy and Cyber Sunday, but failed to win each time. He was originally scheduled to be in the WWE Championship match at Survivor Series, but, in storyline, was found unconscious in his hotel, allowing the returning Edge to replace him in the match and win the title. At Armageddon, Hardy defeated Edge and Triple H in a triple threat match to capture the WWE Championship, his first world championship.
In January 2009, Hardy's next storyline led to his involvement in scripted accidents, including a hit-and-run automobile accident and an accident involving his ring entrance pyrotechnics. At the 2009 Royal Rumble, Hardy lost his WWE Championship to Edge after Hardy's brother, Matt, interfered and turned on Hardy, hitting with a steel chair. The buildup to this feud involved Matt implying that he was responsible for all of Hardy's accidents over the past few months, and at WrestleMania XXV, Matt defeated Jeff in an Extreme Rules match and in a stretcher match on the April 10 episode of SmackDown. In a rematch at Backlash, however, Hardy defeated Matt in an "I Quit" match to end the feud.
On the following episode of SmackDown, Hardy won a fatal four-way elimination match to become the number one contender for Edge's World Heavyweight Championship at Judgment Day, but lost to Edge after Matt interfered and attacked him. Hardy then defeated Edge in a non-title match on the following SmackDown to earn the right to choose the stipulation for their rematch at Extreme Rules and chose a ladder match. At the event, Hardy won the match to become World Heavyweight Champion for the first time. Immediately after the match, CM Punk cashed in his second Money in the Bank briefcase, which gave him a guaranteed world championship match at any time he wanted, and defeated Hardy to win the championship. He received his rematch against Punk in a triple threat match also involving Edge on the June 15 episode of Raw, but failed to win. Hardy got another rematch at The Bash, and won the match via disqualification after Punk kicked the ref in the back while feigning an eye injury with Punk still retaining the title. At Night of Champions, however, Hardy defeated Punk to win the championship for the second time. He made his first successful title defense five days later on SmackDown by defeating John Morrison. After the match, he was attacked by Punk, who invoked his rematch for the following week, where Hardy retained the championship after interference from Matt Hardy, who was the special guest enforcer. Punk again attacked Hardy post-match, resulting in Teddy Long announcing a Tables, Ladders, and Chairs match between the two for the World Heavyweight Championship at SummerSlam. At the pay-per-view, Hardy lost the title back to Punk. On the August 28 episode of SmackDown, Hardy lost to Punk in a steel cage rematch for the World Heavyweight Championship, resulting in Hardy leaving WWE, in storyline, per the pre-match stipulation. This storyline was put in place to allow Hardy to leave WWE to heal his injuries, including a neck injury.
On April 2, 2017, at WrestleMania 33, Jeff made his surprise return to WWE, along with his brother Matt, being added as last-minute participants in the ladder match for the Raw Tag Team Championship against the teams of Luke Gallows and Karl Anderson, Cesaro and Sheamus, and Enzo Amore and Big Cass. The Hardy Boyz emerged victorious, marking it their seventh tag team title reign in WWE, their first win as a team at WrestleMania as well as Jeff's first victory at WrestleMania. Jeff also became the second person, after Chris Jericho, to win all Grand Slam eligible titles under the original format. The next night on Raw, The Hardy Boyz successfully defended the Raw Tag Team Championship against Luke Gallows and Karl Anderson. At Payback, the Hardy Boyz retained their championships against Cesaro and Sheamus. After the match, they were attacked by Cesaro and Sheamus. The next night on Raw, the villainous Cesaro and Sheamus would explain their actions, claiming the fans were more supportive of 'novelty acts' from the past like The Hardy Boyz, who they feel didn't deserve to be in the match at WrestleMania. Subsequently, at Extreme Rules, the Hardy Boyz lost the titles in a steel cage match against Cesaro and Sheamus, and failed to regain it back the following month at the inaugural Great Balls of Fire event. On August 20 on the SummerSlam pre-show, The Hardy Boyz teamed with Jason Jordan against The Miz and The Miztourage (Curtis Axel and Bo Dallas) in a losing effort.
On the August 28 episode of Raw, Hardy won a 15-man battle royal by last eliminating Jason Jordan to become the #1 contender for the Intercontinental Championship. Hardy was unsuccessful in his challenge the following week. In September, Hardy suffered a shoulder injury and it was reported that the injury would sideline him for four to six months. He briefly returned on the Raw 25 Years edition of Monday Night Raw in a poker segment also involving the APA, and other legends. Hardy made a cameo appearance in a taped segment for the March 19 episode of Raw, during the Ultimate Deletion between Matt and Bray Wyatt, allowing his brother Matt to pick up the victory.
Hardy returned on the April 9, 2018 episode of Raw the night after WrestleMania 34, where he assisted Seth Rollins and Finn Bálor in a confrontation with The Miz and The Miztourage. Later the night, after an encountering his brother Matt as well as Bray Wyatt. Hardy, Rollins, and Bálor defeated The Miz and The Miztourage in a 6-man tag team match. The following week on the April 16 episode of Raw, Hardy won the United States Championship for the first time in his WWE career, from Jinder Mahal, and making him the second person (after Chris Jericho) to complete the modern Grand Slam after completing the original format separately. The next day on the April 17 episode of SmackDown Live, Hardy was traded to the SmackDown brand as part of the 2018 WWE Superstar Shake-up and took the United States Championship with him. Hardy defeated Shelton Benjamin in his first match on the SmackDown brand since 2009. At the Greatest Royal Rumble on April 27, Hardy successfully defended the United States Championship in a rematch against Mahal. Following the event, Hardy entered a feud with Randy Orton, whom he retained the title against at Backlash on May 6.
On the May 8 episode of SmackDown, Hardy would be defeated by The Miz in a qualifying match for the 2018 Money in the Bank ladder match. Two weeks later on the May 22 episode of SmackDown, Hardy faced Daniel Bryan in an attempt to earn another Money in the Bank qualifying match, but was defeated. On the June 12 edition of SmackDown, Hardy would face Shinsuke Nakamura in their first ever singles match in WWE. Nakamura would end the bout with a low blow, followed by a Kinshasa, with Nakamura shouting the 10 count, alluding to his upcoming Last Man Standing WWE Championship match against champion AJ Styles at the Money in the Bank pay-per-view. The following week on SmackDown, Hardy would appear wearing face paint and white contact lenses, calling out Nakamura.
On July 15 at the Extreme Rules pay-per-view, Hardy dropped the United States Championship to Shinsuke Nakamura in only six seconds after Nakamura struck Hardy with a low blow before the match started, ending Hardy's reign at 90 days. After the match, Randy Orton returned from injury and attacked Hardy with a second low blow. Hardy received his rematch against Nakamura on the July 17 episode of SmackDown, winning by disqualification after Orton interfered; however, Nakamura retained the championship. As a result, Hardy received another rematch at SummerSlam, but was again defeated by Nakamura. On the SmackDown after SummerSlam, Hardy faced Orton in a grudge match that Orton won via DQ after Hardy low-blowed him. Hardy lost to Orton in a Hell in a Cell match at the namesake event on September 16 and again on 23 October episode of SmackDown, thus ending their feud. After nearly a month off, Hardy returned on the October 9 episode of SmackDown, defeating Samoa Joe via referee stoppage to qualify for the WWE World Cup Tournament at Crown Jewel. At the event, Hardy lost to The Miz, in the first round of the tournament.
On the November 6 episode of SmackDown, Hardy lost to Samoa Joe in an attempt to join Team SmackDown Live at Survivor Series. On the November 13 episode of SmackDown, Hardy defeated Andrade "Cien" Almas to earn a spot on Team SmackDown Live at Survivor Series in a second chance match after Daniel Bryan was dropped from the team following his WWE Championship victory. However, Team SmackDown was unsuccessful at the event. On the November 27 episode of SmackDown, WWE celebrated Jeff Hardy's 20th Anniversary in the WWE after debuting for the first time as a contracted star in 1998. This led to Samoa Joe interrupting and attacking Hardy. Hardy participated in the Royal Rumble match at the namesake event but was eliminated by Braun Strowman and Drew McIntyre.
On the February 26 Episode SmackDown Live, Jeff reunited with a returning Matt in a winning effort against The Bar. A week later, The Hardy Boyz assisted Ricochet and Aleister Black as they were attacked by Rusev and Shinsuke Nakamura. This led to The Usos calling the Hardy Boyz out on the March 12 episode of SmackDown Live. At WrestleMania 35, Hardy participated in the Andre the Giant Memorial Battle Royal and lasted until the final four before being eliminated alongside brother Matt by eventual winner Braun Strowman. Two nights later on the April 9 edition of SmackDown, The Hardy Boyz defeated The Usos to win the SmackDown Tag Team Championship, their ninth tag team championship together in the WWE. After the match and winning the SmackDown Tag Team Championship, they were attacked by Lars Sullivan. On the April 30 episode of Smackdown Live, The Hardy Boyz vacated the SmackDown Tag Team Championships because of Jeff's leg injury. WWE announced that Hardy would be out of action for 6 to 9 months.
On the March 13, 2020 episode of SmackDown, Hardy returned from injury, defeating King Corbin. On the Money in the Bank pre-show, Hardy was victorious over Cesaro. He then began a feud with Sheamus over comments that the latter made, defeating him in the first round of the Intercontinental Championship tournament on the May 22 episode of SmackDown. On the May 29, 2020 episode of SmackDown, Hardy was "arrested" after crashing his car into Elias, however later in the episode, Hardy would cause a distraction for Sheamus, costing him a match over Daniel Bryan, and attacked Sheamus after the match. The feud led to a match at Backlash between Hardy and Sheamus, which Hardy lost. On the July 24 episode of SmackDown, Hardy defeated Sheamus in a Bar Fight.
On the August 14 episode of SmackDown, Hardy issued a challenge to the Intercontinental Champion AJ Styles for the title. The following week on SmackDown, he defeated AJ Styles to win the Intercontinental Championship for the fifth time. At Clash of Champions, Hardy lost the title to Sami Zayn in a triple threat ladder match, which included Styles. As part of the 2020 draft in October, Hardy was drafted to the Raw brand. On the October 12 episode of Raw, Jeff Hardy would face Seth Rollins and AJ Styles in a triple threat match, but a returning Elias would attack Hardy, thus starting a feud between Elias and Hardy. On the October 16 episode of SmackDown, Hardy would lose a match to Lars Sullivan. On the October 19 episode of Raw, Hardy would attack Elias during his concert. At Hell in a Cell, Hardy would lose to Elias after he snapped and hit Elias with a guitar, giving Elias the win via disqualification . On the October 26 episode of Raw, Hardy would lose a Survivor Series qualification match to AJ Styles. On the November 2 episode of Raw, Hardy would defeat Elias in a "Guitar on a Pole" match. On the November 9 episode of Raw, Hardy would compete in a last chance qualifying match for Team Raw agianst Riddle and Elias, but would lose and Riddle would get the win. On the November 30 episode of Raw, Hardy would defeat Elias and a Symphony of Destruction match.
On the December 7 episode of Raw, before his match with Bobby Lashley, Riddle would approach Jeff Hardy in order to form a team with Hardy. Hardy would seemingly accept before going out and losing his match against Bobby Lashley. On the December 14 episode of Raw, Hardy would team with The New Day in a losing effort against The Hurt Business. On the December 21 episode of Raw, Hardy and Riddle would be defeated by The Hurt Business' Bobby Lashley and MVP. On the December 28 episode of Raw, Hardy, Riddle, and The New Day would lose to The Hurt Business. On the January 4 episode of Raw, Hardy would be defeated by Randy Orton. On the January 11 episode of Raw, Hardy would face Jaxson Ryker in a losing effort, but would then challenge Elias to a match where he would be victorious. On the January 18 episode of Raw, Hardy would declare for the Royal Rumble. Hardy would then face Jaxson Ryker and would win via disqualification. At the Royal Rumble, Hardy would be the first person eliminated from the match. On the February 1 episode of Raw, Hardy would team with a returning Carlito and defeat Jaxson Ryker and Elias. On the February 8 episode of Raw, WWE Official Adam Pearce would announce that Hardy would be apart of the Elimination Chamber match for Drew McIntyre's WWE Championship. After the announcement, Hardy would face AJ Styles but would be defeated. At Elimination Chamber, Hardy would be unsuccessful in winning as he was eliminated by Dew McIntyre.
On the July 19 episode of Raw, Hardy brought back his "No More Words" entrance theme for the first time since his 2009 departure, and defeated NXT Champion Karrion Kross, becoming the first man in WWE to defeat Kross by pinfall. On the September 13 Raw, Hardy challenged Damian Priest for the WWE United States Championship, but lost. On the September 20 episode of Raw, Hardy would defeat Sheamus to be added to the United States title match at Extreme Rules. At the event, Hardy would fail to win the title as Damian Priest would retain.
As part of the 2021 Draft in October, Hardy was drafted to the SmackDown brand. On December 9, Hardy was released from his contract.