Kelly debuted in World Wrestling Entertainment (WWE) in 2006 for the ECW brand. She made her debut on the first episode of the weekly television program on June 13, 2006. Her character, an exhibitionist, was introduced performing a striptease for the crowd. The next week, while performing another striptease, Kelly was interrupted by her on-screen boyfriend, Mike Knox, who came to the stage and covered her with a towel before dragging her backstage. Her stripping became a weekly segment known as Kelly's Exposé and usually followed the same routine; Kelly would dance and strip until she was stopped by Knox. Knox began forcing Kelly to accompany him to ringside so he could keep an eye on her, making her his de facto valet. As a result, she found herself involved in the feud developing between Knox and his tag team partner Test and the team of Tommy Dreamer and The Sandman. This included her being inadvertently hit with a cane by Sandman when Knox used her as a shield. She made her ECW in-ring debut on the August 22 episode as part of a six-person mixed tag team match, in which she, Knox, and Test lost to Dreamer, Sandman, and Torrie Wilson.
Kelly and Knox progressed into a storyline with CM Punk in September, in which Kelly developed a liking for Punk, flirting with him and watching his matches, and Knox became increasingly jealous. This led to a match between Knox and Punk, during which Kelly cheered for Punk. At December to Dismember, Kelly and Knox faced Ariel and Kevin Thorn in a mixed tag team match, during which Knox refused to tag in before leaving her. On the following episode of ECW, Kelly defeated Ariel with a roll-up in her first singles match. Afterward, Knox made his way to the ring with flowers, but ended up performing his signature swinging reverse STO on her, ending their relationship and giving her a scripted injury—removing her from television for six weeks.
She returned on January 16, 2007, to announce she was newly single and bringing back Kelly's Exposé. The following week, she joined forces with Layla and Brooke to form Extreme Exposé. The trio performed a weekly dance segment on ECW for the next several months. On November 1, Brooke was released from her WWE contract, and Extreme Exposé dissolved as a group. This left Kelly and Layla to enter an ongoing rivalry with more active wrestling roles. On the October 29 episode of Raw, Kelly won a battle royal to earn a match against the WWE Women's Champion, Beth Phoenix. Kelly lost the subsequent match the following week on Raw. Kelly continued to feud with Layla, and they were on opposite sides of a 10-Diva tag team match at Survivor Series, which Kelly's team won. In April 2008, Kelly was part of the losing team in a five-on-five Divas match at the Backlash pay-per-view.
In July, Kelly was moved to the Raw brand and debuted for the brand by teaming with Mickie James to defeat Layla and Jillian Hall. She quickly became involved in a feud with Beth Phoenix, facing her on multiple occasions in both singles and tag team matches with a variety of partners, including Mickie James and Candice Michelle. In September, Kelly transitioned into a feud with Phoenix's ally, Jillian Hall. At the Survivor Series pay-per-view in November, Kelly was part of the victorious team in a five-on-five elimination match. During the match, she eliminated Victoria, before being eliminated by Maryse. The following month at the Armageddon pay-per-view, Kelly teamed with Maria, Michelle McCool, and James in a winning effort against Hall, Maryse, Victoria, and Natalya.
On the May 18 episode of Raw, Kelly won a battle royal to become the number one contender to the WWE Divas Championship. The following week, she challenged Maryse for the championship and won by disqualification, with Maryse retaining the title. Kelly lost a subsequent rematch by pinfall two weeks later on June 8. In June, she competed in a fatal four-way match to determine the number one contender, but the match was won by James. Throughout the remainder of mid-2009, Kelly unsuccessfully competed in several number one contender matches.
At the Bragging Rights pay-per-view in October, Kelly, Gail Kim, and Melina comprised Team Raw, but lost to Team SmackDown (Phoenix, Natalya, and McCool). The following month at the Survivor Series pay-per-view, Kelly participated in a five-on-five elimination match, which her team won. She eliminated Layla before being eliminated by Phoenix. In January 2010, Kelly participated in the tournament to determine a new Divas Champion, after Melina was forced to vacate the championship due to injury. She was eliminated by Alicia Fox in the first round. Throughout early 2010, Kelly was involved in several backstage segments with the guest hosts of Raw. At WrestleMania XXVI, Kelly teamed with Phoenix, Kim, James, and Eve Torres in a losing effort to McCool, Layla, Maryse, Fox, and Vickie Guerrero. The following night on Raw, the teams faced off in a rematch with the opposite result. The following week, Kelly took part in a 10-Diva Dress to Impress battle royal, to determine the number one contender for Maryse's Divas Championship, but the match was won by Torres.
During the 2010 WWE Draft on April 26, Kelly was drafted to the SmackDown brand, making her the first drafted female wrestler on television. She quickly began to feud with LayCool (Michelle McCool and Layla), and gained an ally in Tiffany. After defeating both Layla and McCool in singles matches, she received her first WWE Women's Championship match at the Money in the Bank pay-per-view in July, but was unsuccessful. On August 31, Kelly announced that she would be a mentor on season three of NXT, with Naomi as her rookie. Throughout the second half of 2010, Kelly continued to feud with LayCool, and gained an ally in Natalya in October. In November, Kelly's NXT rookie, Naomi was named runner-up to the winner, Kaitlyn, during the season finale.
On January 30, 2011, at the Royal Rumble, Kelly prevented the Acting General Manager Vickie Guerrero from interfering in the World Heavyweight Championship match between Edge and Dolph Ziggler. On the following SmackDown, Kelly and Edge defeated LayCool and Ziggler in a two-on-three handicap match to retain Edge's World Heavyweight Championship. Afterward, Guerrero fired Kelly in storyline. At the Elimination Chamber pay-per-view later that month, Kelly was re-hired by SmackDown General Manager Teddy Long, and made her return by attacking Guerrero. She was stopped by LayCool, who were in turn stopped by Trish Stratus. The next week, on SmackDown, Kelly and Edge defeated Guerrero and Drew McIntyre in a mixed tag team match, causing Guerrero to be fired in storyline per the pre-match stipulation.
On April 26, Kelly was drafted back to the Raw brand as part of the 2011 supplemental draft, where she received a push and began feuding with The Bella Twins. On May 22 at the Over the Limit pay-per-view, Kelly unsuccessfully challenged Brie Bella for the WWE Divas Championship. The following month, on the Power to the People special edition of Raw on June 20, Kelly won a fan vote to determine the challenger for the Divas Championship that night. Kelly went on to win her first WWE Divas Championship by defeating Brie Bella. Her win later garnered her a Slammy Award for Divalicious Moment of the Year. At the Money in the Bank pay-per-view in July, Kelly made her first title defense by defeating Bella in a rematch. On August 1, Phoenix won a battle royal to become the number one contender to Kelly's championship, and afterward attacked Kelly to provoke a feud. Kelly successfully defended her championship against Phoenix at both SummerSlam and Night of Champions. Kelly lost the championship to Phoenix at Hell in a Cell in October, ending her reign at 104 days. In subsequent rematches on SmackDown and at Tables, Ladders & Chairs, Kelly failed to regain the title.
Kelly spent early 2012 participating in several tag team matches. At WrestleMania XXVIII in April, Kelly and Maria Menounos defeated Beth Phoenix and Eve in a tag team match. In June, WWE granted Kelly a period of time off, and she returned on Raw on August 6, defeating Eve. On September 28, 2012, Kelly was released from her WWE contract.
Kelly returned to WWE on February 13, 2017, by being featured in a backstage interview for WWE's official website during Raw. She later appeared during WrestleMania weekend, including at the Hall of Fame induction ceremony, and appeared on an episode of the WWE Network exclusive Table for 3.
On January 22, 2018, Kelly appeared at the Raw 25 Years special, being honored as one of the historic women of WWE. A few days later, on January 28 at the Royal Rumble event, Kelly competed in the first women's royal rumble match, where she entered at number 19, and was eliminated by Nia Jax. In October 2018, Kelly participated in a battle royal at WWE's first all-female pay-per-view WWE Evolution; she was eliminated by Mandy Rose.
On July 22, 2019, Kelly returned during Raw Reunion, where she pinned Gerald Brisco backstage to become the first female 24/7 Champion. With this win, Kelly Kelly became the first woman to hold both the WWE Divas Championship and the 24/7 Championship. Kelly then lost the title to Candice Michelle, with Melina as the referee. She returned to the ring again on the January 26, 2020 Royal Rumble event, entering at number twenty-one before being eliminated by Charlotte Flair. Kelly appeared on Raw the following night on January 27, 2020 in a backstage segment with Street Profits. On November 22, Kelly appeared on WWE's Watch Along by watching and recapping Survivor Series.
On the January 7, 2022 episode of SmackDown, Kelly was announced as a participant in the women's Royal Rumble match at the Royal Rumble, marking her third appearance as a surprise entrant. She entered at number four and was quickly eliminated by Sasha Banks.