In July 2012, it was reported that Neville had signed a contract with WWE. He joined WWE's developmental territory NXT, and made his television debut using the ring name Adrian Neville on the January 16, 2013 episode of NXT, where he defeated Sakamoto.
Together with Oliver Grey, the English duo won a tournament to crown the inaugural NXT Tag Team Champions by defeating The Wyatt Family (Luke Harper and Erick Rowan) in the finals on the February 13 episode of NXT. Neville and Grey, now billed as British Ambition, had earlier defeated 3MB (Heath Slater and Drew McIntyre) in the first round and Kassius Ohno and Leo Kruger in the semi-finals. With Grey out injured with a torn ACL (in storyline inflicted by the Wyatt Family), Neville chose Bo Dallas as his new partner in April. On April 24 on NXT, Neville lost to Antonio Cesaro while challenging for his United States Championship. On the May 8 episode of NXT, Neville and Dallas failed in their first defense of the tag titles when they lost them to the Wyatt Family.
On the May 29 episode of NXT, Neville competed in an NXT Championship number one contender battle royal, eliminating Mason Ryan and Bray Wyatt (who had eleven and two eliminations respectively) to make it to the final two participants, but his former tag partner Dallas eliminated him to win the match. Later, Dallas won his title match to become NXT Champion. Neville continued his feud with the Wyatt Family by losing to them in two six-man tag matches, once while teaming with Corey Graves and Kassius Ohno, and once with Graves and William Regal. On June 20, Neville regained the NXT Tag Team Championship from the Wyatt Family with a new partner in Graves. On the August 6 episode of NXT, Neville faced Dean Ambrose for his United States Championship, which Ambrose retained when the other members of The Shield caused a disqualification. Neville and Graves lost the titles to The Ascension (Conor O'Brian and Rick Victor) in September. Following this, the two feuded after failing to regain the title.
Neville first became number one contender to the NXT Championship on the November 27 episode of NXT by defeating Sami Zayn, after both men previously tied a beat the clock challenge. Neville faced former tag partner Bo Dallas for the title on the next episode and won by countout, which meant that the title did not change hands. Two episodes later, Neville faced Dallas again for the title in a lumberjack match, but lost when lumberjack Tyler Breeze interfered. Neville once again became number one contender after Dallas failed to defeat Neville in a beat-the-clock challenge match on the January 22 episode of NXT that arose due to Dallas' boasting. At NXT Arrival, Neville won the NXT Championship from Dallas in a ladder match. A rematch was scheduled for the March 20 episode of NXT, which he won after debuting a new finisher, the imploding 450° splash.
Neville's first feud as champion began following a non-title match against Brodus Clay, where Neville won by countout. The feud ended with Neville scoring a no disqualification match victory over Clay to successfully defend the NXT Championship. At NXT TakeOver, Neville successfully defended the NXT Championship against Tyson Kidd. Two weeks later, Neville retained his championship against Kidd again after Natalya prevented Kidd from using a chair. On the July 31 episode of NXT, he successfully defended his title against Tyler Breeze by disqualification as Tyson Kidd attacked Neville after being super kicked by Neville. On September 8, Neville made his first appearance on Raw as part of an NXT showcase match to promote NXT TakeOver: Fatal 4-Way, he teamed with Sami Zayn to defeat Kidd and Breeze in a tag team match. On September 11 at the NXT TakeOver: Fatal 4-Way event, Neville successfully defended his NXT Championship against Sami Zayn, Tyler Breeze and Tyson Kidd in a fatal four-way match. On December 4, Neville became the longest reigning NXT Champion of all time, surpassing the record set by Bo Dallas (which was surpassed by Finn Bálor in April 2016). Later on December 11 at the NXT TakeOver: R Evolution event, Neville lost the championship to Zayn, ending his reign at 287 days. When Neville offered a handshake, Zayn kicked it away and instead hugged Neville in respect.
The following week on the December 18 episode of NXT, Neville faced Kevin Owens, but the match ended in a double countout. Owens powerbombed Neville into the apron after the match. Neville received a rematch on the January 15, 2015 episode of NXT, but failed to regain the title. Neville went on to compete in an NXT Championship number one contender's tournament, defeating Tyson Kidd in the quarterfinals on January 28 and Baron Corbin in the semifinals on February 4, but lost in the finals to Finn Bálor at NXT TakeOver: Rival.
On the March 30, 2015 episode of Raw, he made his main roster debut, under the shortened ring name Neville, defeating Curtis Axel. He then defeated Bad News Barrett at the Extreme Rules pay-per-view the following month. Following this, Neville competed in the 2015 King of the Ring tournament, where he was defeated by Barrett in the finals. Following this, Neville would begin a feud with former rival Bo Dallas, setting up a match at Elimination Chamber, which Neville won.
Neville would then enter a feud with Stardust in a comic book inspired rivalry. At SummerSlam on August 23, Neville would team up with actor Stephen Amell, defeating the team of Stardust and Barrett. At Night of Champions in September, Neville would team with The Lucha Dragons (Kalisto and Sin Cara) in a loss to Stardust and the Ascension. On the Survivor Series pre-show, Neville would compete in a traditional Survivor Series match, teaming with The Dudley Boyz (Bubba Ray Dudley and D-Von Dudley), Goldust and Titus O'Neil in a victory over Stardust, The Ascension, The Miz and Bo Dallas. On the December 21 episode of Raw, Neville won the Slammy Award for "Breakout Star of the Year".
At the Royal Rumble on January 24, 2016, Neville competed in his first Royal Rumble match as the number 16 entrant, lasting over ten minutes before being eliminated by Luke Harper. In March 2016, Neville injured his ankle during a match with Chris Jericho on Raw, rendering him out of action for an estimated two to three months and forcing him to miss WrestleMania 32, for which he was scheduled to compete at.
On July 19, at the 2016 WWE draft, Neville was drafted to Raw. On the July 25 episode of Raw, Neville made his televised return, defeating Curtis Axel. Neville teamed with Sami Zayn to defeat The Dudley Boyz (Bubba Ray Dudley and D-Von Dudley) at SummerSlam. The following night on Raw, Neville failed to defeat Kevin Owens to qualify for a fatal four-way elimination match for the vacant WWE Universal Championship after the interference of Chris Jericho. On the October 31 episode of Raw, Neville participated in a battle royal for a spot on Team Raw at Survivor Series, but was eliminated by eventual winner Braun Strowman.
On December 18 at Roadblock: End of the Line, Neville returned to seemingly congratulate Cruiserweight Champion Rich Swann after his match, only to attack Swann and his opponent TJ Perkins, turning heel for the first time in his WWE career and joining the Cruiserweight division. The following night on Raw, Neville cemented his villainous turn after claiming that the fans only cheered him because he was "vulnerable or small" and proceeded to attack Swann along with Brian Kendrick after he interrupted him, followed by Perkins after he attempted to save Swann. Over the coming weeks, Neville would defeat multiple Cruiserweights in singles competition including Perkins, Cedric Alexander, Lince Dorado and Swann in a non-title match. On January 29, 2017 at the Royal Rumble, Neville defeated Swann to capture the Cruiserweight Championship for the first time, marking his first title win on the main roster. Neville then started a feud with Jack Gallagher, and successfully defended his title at Fastlane against Gallagher.
The following night on Raw, Neville defended his title against Swann successfully. After the match, Austin Aries seemingly appeared to interview Neville only to attack him and start a feud between the two. At WrestleMania 33, Neville would defeat Aries in his WrestleMania in-ring debut. Aries won a fatal-four-way match two days later on 205 Live to earn a rematch against Neville at Payback, which Neville lost by disqualification, retaining the title as a result. Around this time, Neville formed an alliance with TJ Perkins, who would assist him in his rivalry with Aries, in exchange for a promised championship opportunity. Neville defeated Aries again in a submission match at Extreme Rules to retain the Cruiserweight Championship, concluding their rivalry in the process. He ended his alliance with Perkins the following night, attacking him and later going on to successfully defend his championship against him on the June 6th episode of 205 Live.
Neville then began feuding with Akira Tozawa, who was granted a championship match for Great Balls of Fire by Titus O'Neil, in which Neville retained the title. He was also set to defend his title against Tozawa for the second time at SummerSlam, until the August 14 episode of Raw, where Neville lost the championship to Tozawa, ending his record setting reign at 197 days. However, Neville won the title back from Tozawa on the SummerSlam pre-show, making him the first-ever two-time Cruiserweight Champion. On the August 21 episode of Raw, it was announced that Tozawa had invoked the rematch clause. Neville defeated Tozawa by submission on the August 22 episode of 205 Live to end their feud.
Afterwards, he was confronted by Enzo Amore, the latest member of the Cruiserweight division. On September 24 at No Mercy, Neville dropped the title to Amore after being hit with a low blow while the referee was distracted. The following night on Raw, while Amore was disparaging the cruiserweight division, Neville spoke on behalf of the cruiserweights and attempted to attack Amore. Amore revealed he had a no-contact clause, which prevented any of the cruiserweights of receiving a future title shot should they attack him, but Neville attacked him nonetheless after the cruiserweights prevented Amore from leaving. The next night on 205 Live, after Neville defeated Ariya Daivari, he was attacked by Amore with a crutch. This would be Neville's final appearance on WWE programming.
On October 9, Neville walked out on Raw, on which he was scheduled to face Enzo Amore. On August 24, 2018, it was reported that Neville was no longer under contract.