When NXT was rebranded as WWE's developmental system in August 2012, Harper made his television debut on the November 7 NXT as a Luke Harper, a follower of Bray Wyatt, who introduced Harper as the "first son" of The Wyatt Family. The Wyatt Family later also came to include Wyatt's "second son" Erick Rowan, with whom Harper formed a tag team. The two defeated Percy Watson and Yoshi Tatsu in their first match together on the January 9, 2013 NXT. On the January 23 NXT, Harper and Rowan again defeated Watson and Tatsu in the opening round of the NXT Tag Team Championship tournament. Following a win over Bo Dallas and Michael McGillicutty in the semi-finals with Wyatt's interference, Harper and Rowan were defeated in the finals of the tournament by Adrian Neville and Oliver Grey. Harper defeated Neville on the March 20 NXT. On the May 2 NXT, Harper and Rowan won a triple threat elimination tag match by last pinning Neville. On the May 8 NXT (taped May 2), Harper and Rowan defeated Neville and Bo Dallas, filling in for the injured Grey, to win the NXT Tag Team Championship. After retaining the title against Corey Graves and Kassius Ohno on the June 5 NXT, Harper and Rowan lost the NXT Tag Team Championship to Neville and Graves on the July 17 NXT (taped June 20).
From the May 27 Raw, WWE aired vignettes promoting the upcoming debut of the Wyatt Family. The vignettes showed the Wyatt Family's backwoods origins. On the July 8 Raw, the Wyatt Family made their debut by assaulting Kane. Harper made his WWE in-ring debut on the July 26 SmackDown, where he and Rowan defeated Tons of Funk (Brodus Clay and Tensai). Over the next few months, Harper and Rowan went on a winning streak over many teams, until Cody Rhodes and Goldust handed them their first loss on the October 11 SmackDown. After the Wyatt Family started feuding with CM Punk and Daniel Bryan, Harper wrestled two singles matches, losing to Punk on the November 4 Raw and to Bryan via disqualification on the November 8 SmackDown. In early 2014, The Wyatt Family feuded with The Shield, defeating them at Elimination Chamber, while also supporting Bray Wyatt in his feud with John Cena through WrestleMania XXX. Through Wyatt's feud with Cena, Harper and Rowan also started their own feud with the WWE Tag Team Champions The Usos (Jey Uso and Jimmy Uso), who supported Cena in the feud. Harper and Rowan went on to unsuccessfully challenge the Usos for the WWE Tag Team Championship at Money in the Bank and in a two out of three falls match at Battleground.
Beginning on September 29, vignettes were shown of Harper and Rowan being "set free" by Wyatt, marking the dissolution of the Wyatt Family and the transition of its members into singles competition. After a further series of video vignettes aimed at Dolph Ziggler, Harper made his return to TV during the closing moments of the November 10 episode of Raw, throwing an unconscious Ziggler at Triple H and Stephanie McMahon's feet and expressing his desire to join their team at Survivor Series. The following week on Raw, Harper officially joined Team Authority. Immediately after, Harper was awarded an impromptu match for the WWE Intercontinental Championship against Dolph Ziggler, which, after interference from Seth Rollins, Harper won to capture his first title in WWE. At Survivor Series, Harper was eliminated by Ziggler. As punishment for his affiliation with The Authority, Harper was forced to defend the Intercontinental Championship against Dean Ambrose on the November 24 Raw and successfully retained the title after getting himself disqualified. Harper lost the title back to Ziggler in a ladder match at TLC: Tables, Ladders and Chairs, his reign ending at 27 days, and failed to regain the title in a rematch on the December 22 Raw. On January 25, 2015, Harper entered the Royal Rumble match at No. 4, and was eliminated by Bray Wyatt. Beginning in early March, Harper was involved into a storyline where he was one of many wrestlers stealing Bad News Barrett's Intercontinental Championship belt from Barrett and each other. This led to a seven-man ladder match for the title on March 29 at WrestleMania 31, which was won by Daniel Bryan. The match led to a new feud between Harper and Dean Ambrose, with Harper losing a Chicago Street Fight between the pair at Extreme Rules. On the April 27 Raw, Harper took part in the 2015 King of the Ring tournament, but eliminated by Neville in the first round.
In early May, Harper revived his alliance with Erick Rowan. After Rowan suffered an injury, Harper reunited with Bray Wyatt on July 19 at Battleground by helping him defeat Roman Reigns. This led to a tag team match between Harper and Wyatt against Reigns and Dean Ambrose at SummerSlam, which The Wyatt Family lost after Reigns pinned Wyatt. The following night on Raw, Braun Strowman joined Harper and Wyatt as the new third member of the Wyatt Family. At Night of Champions, The Wyatt Family defeated Reigns, Ambrose and Chris Jericho in a six-man tag team match. On the October 19 Raw, Erick Rowan returned to The Wyatt Family when he filled in for Harper (who was unable to show for personal reasons).
The Wyatt Family then got involved in a feud with Kane and The Undertaker, which built to a tag team match on November 22 at Survivor Series, where the two defeated Harper and Wyatt. The next night on Raw, Harper teamed with Wyatt again to defeat The Dudley Boyz, igniting a new feud. Over the next weeks, Tommy Dreamer and Rhyno joined The Dudley Boyz in the feud, leading to an eight-man tag team tables match at TLC: Tables, Ladders and Chairs on December 13, where Harper, Wyatt, Rowan and Strowman were victorious. On January 24, 2016, Harper competed in the Royal Rumble with fellow Wyatt Family members and he was eliminated by Brock Lesnar, but returned to the ring later on with the Wyatts to eliminate Lesnar. On March 21, Harper suffered a knee injury during a dark match on Raw, sidelining him for five to six months. After getting an MRI, it was revealed that he had dislocated his patella and tore his medial patellofemoral ligament. Because of his injury, Harper was not drafted to either Raw or SmackDown in the 2016 WWE draft.
Harper returned to the ring on October 5, teaming with Kevin Owens against Sami Zayn and Seth Rollins at a Raw house show in Santiago, Chile. Four days later, Harper returned in the final match of the SmackDown brand pay-per-view No Mercy, helping Bray Wyatt defeat Randy Orton by distracting Orton, thus joining the SmackDown roster. On December 4 at TLC: Tables, Ladders & Chairs, Wyatt and Orton, who had recently joined The Wyatt Family, captured the SmackDown Tag Team Championship, and three days later it was announced that Harper had been sanctioned as champion as well, making him eligible to defend the title under the "Freebird Rule". On the December 13 episode of SmackDown, Harper failed to become the number one contender for the WWE Championship in a four-way elimination match, which was won by Dolph Ziggler. The Wyatt Family, represented by Harper and Orton, lost the SmackDown Tag Team Championship to American Alpha (Chad Gable and Jason Jordan) in a four-way elimination match on the December 27 episode of SmackDown. After the match, Harper and Orton showed tension over the loss. After Orton and Wyatt unsuccessfully challenged American Alpha for the title on the January 10, 2017 episode of SmackDown, Harper and Orton shoved each other, which led to Harper accidentally superkicking Wyatt. Harper and Orton continued having problems with each other, leading to a match between the two on the January 24 episode of SmackDown, where Orton was victorious. After the match, Wyatt laid Harper out with the Sister Abigail.
During the Royal Rumble on January 29, Harper entered as number 25, attacking both Wyatt and Orton and eliminating Apollo Crews, before being eliminated by Goldberg. Over the next two weeks, Harper turned face by coming to WWE Champion John Cena's aid in his confrontations with Wyatt and Orton on SmackDown. At Elimination Chamber on February 12, Harper was defeated by Orton in a singles match. Due to Royal Rumble winner Orton refusing to face Wyatt for the WWE Championship at WrestleMania 33, a battle royal was set up on the February 21 SmackDown to determine a new number one contender, which saw Harper and AJ Styles become the co-winners by eliminating each other at the same time, setting up a singles match between the two for the following week, where Styles was victorious. After a month of absence, Harper returned with a new look on the March 28 episode of SmackDown, losing to Bray Wyatt. On April 2 on the WrestleMania 33 kickoff show, Harper took part in the André the Giant Memorial Battle Royal, from which he was eliminated by Titus O'Neil. A couple days later on SmackDown, Harper aided Orton to fight off Bray Wyatt and a returning Erick Rowan with the two defeating Wyatt and Rowan in a tag team match later on in the main event. The rivalry between Harper and Rowan was seemingly ended at Backlash on May 21, where Harper defeated Rowan. On the July 4 episode of SmackDown, Harper took part in the Independence Day Battle Royal to determine the number one contender for Kevin Owens' United States Championship. He failed to win as the match was eventually won by AJ Styles. After this match, Harper was not seen on television for several months.
Harper returned to television as a heel on the October 10 episode of SmackDown, aligning himself with Rowan once again. The duo were dubbed as "The Bludgeon Brothers" and Harper subsequently dropped the first name Luke from his ring name, thus simply going by Harper. The team wrestled their return match on the November 21 episode, defeating The Hype Bros (Mojo Rawley and Zack Ryder). The following month, the team made their pay-per-view debut at Clash of Champions, defeating Breezango (Tyler Breeze and Fandango).
After months of dominating the SmackDown tag team division, and still undefeated as The Bludgeon Brothers, Harper and Rowan won the SmackDown Tag Team Championship at WrestleMania 34 on April 8, 2018 by defeating The New Day and defending champions The Usos in a triple threat tag team match, their first title as a team on the main roster. They would go on to successfully defend the titles against The Usos at the Greatest Royal Rumble, against Luke Gallows and Karl Anderson at Money in the Bank, and against Team Hell No at Extreme Rules.
At SummerSlam, Harper and Rowan defended their titles against The New Day; they lost by disqualification after Rowan attacked Xavier Woods with a mallet, marking their first loss as The Bludgeon Brothers. Two days later on SmackDown, they lost the titles to The New Day in a no-disqualification match, ending their reign at 135 days. The following day, it was announced that Rowan had suffered a torn right bicep, sidelining him indefinitely. During this time, Harper also underwent surgery due to a wrist injury.
On March 9, 2019, Harper returned to in-ring action, defeating Mojo Rawley at a Raw live event in his hometown of Rochester. He revealed that his return to WWE programming would be at WrestleMania Axxess against Dominik Dijakovic. Following that, he competed in the André the Giant Memorial Battle Royal at WrestleMania 35, but failed to win as he was eliminated by Braun Strowman.
After WrestleMania, Harper wrestled against EC3 in a dark match before an episode of SmackDown Live. After that, on April 16, Harper requested his release from WWE, as he had yet to appear on weekly television. His request was denied by Vince McMahon and WWE.
Luke Harper made his return to WWE programming by attacking Roman Reigns in his match with former partner Erick Rowan at the Clash of Champions pay per view on September 15, 2019. On the following episode of SmackDown, Harper ambushed Daniel Bryan, after a confrontation with Rowan, only to be interrupted by Reigns, who Harper and Rowan laid out as well. At Hell in a Cell, Harper and Rowan were defeated by Bryan and Reigns in a tag team match. Following the loss, Rowan and Harper were once again split up when Rowan was drafted to Raw as part of the 2019 draft, whereas Harper stayed on SmackDown. At Crown Jewel, Harper competed in the pre-show battle royal for a shot at the United States Championship later in the night, but was eliminated. This was Harper's last match on television as he was officially released from WWE on December 8, 2019.
Harper passed away on December 26, 2020.