On August 12, 2014, WWE officially announced that Owens had signed with the promotion. He reported to their developmental territory, NXT, on August 25. Teaser vignettes were aired from the November 20 episode of NXT, promoting Owens' debut for December 11 at the NXT Takeover: R Evolution live special episode. At the event, Owens defeated CJ Parker in his debut match. After Sami Zayn, had won the NXT Championship in the main event, Owens along with the rest of the NXT roster came to the ring to congratulate Zayn, seemingly as a face, before attacking him, establishing himself as a heel in the process. On the December 18 episode of NXT, Owens wrestled former NXT Champion Adrian Neville to a double count-out, and similarly powerbombed Neville after the match. After yet another post-match attack by Owens on Zayn, an irate Zayn demanded a match against Owens, but Owens refused to wrestle unless it was for the championship. Zayn agreed and a title match was set for NXT Takeover: Rival on February 11. At the event, Owens defeated Zayn via doctor stoppage to become the new NXT Champion. On the March 25 episode of NXT, he successfully retained the NXT title against Finn Bálor.
Owens made an appearance on the May 18 episode of Raw by responding to John Cena's United States Championship Open Challenge only to cheap shot him followed by a pop-up powerbomb, setting up a singles match between the two at Elimination Chamber.
At NXT Takeover: Unstoppable, Owens' rematch for the title against Sami Zayn went to a no-contest. Owens continued to beat down an injured Zayn, until the debuting Samoa Joe stopped him. On the May 25 episode of Raw, after Cena retained his United States Championship against Zack Ryder, Owens again attacked Cena while he was celebrating and delivered another pop-up powerbomb. At the event, Owens defeated Cena by clean pinfall. A rematch took place at Money in the Bank, which Cena would win. After the match, Owens pop-up powerbombed Cena onto the ring apron. The following night on Raw he defeated Dolph Ziggler in an open challenge and later attacked musical guest Machine Gun Kelly after his performance. Meanwhile, down in NXT, after weeks of tension between he and Samoa Joe, Owens faced Joe on the June 17 episode of NXT. After the match went to a no-contest, the two would continue to brawl until they had to be separated. On the July 4 WWE Network special event held in Tokyo, Japan, Owens lost the NXT Championship to Finn Bálor, ending his reign at 143 days. At WWE Battleground, Owens submitted to the STF from Cena, and was unable to win the United States Championship. Following his loss to Cena, Owens entered into a feud with Cesaro. On August 22, 2015, at NXT Takeover: Brooklyn, Owens was defeated by Finn Balor in a Ladder Match rematch for the NXT Title. The next night at SummerSlam, Owens defeated Cesaro. Owens defeated Dolph Ziggler on the September 12 episode of Main Event. On the 14 September edition of Raw, it was announced that he will face Ryback for the Intercontinental Championship at Night of Champions. At the event, Owens defeated Ryback after a roll-up to win the Intercontinental Championship - Owens' first title on the main roster. Owens' first successful title defense came at a live special from Madison Square Garden when he defeated Chris Jericho after once again manipulating his opponents vision. At Hell in a Cell, Owens successfully defended his championship against Ryback. The following night on Raw, Owens lost a Fatal 4-Way No. 1 contender's match for the WWE World Heavyweight Championship to Roman Reigns, Alberto Del Rio, and Dolph Ziggler. However, then-champion Seth Rollins injured his knee at a house show in Dublin, vacating the title. A tournament would be held, with the final match taking place at Survivor Series to crown a new champion. Owens defeated Titus O'Neil on the November 9 episode of Raw to advance to the quarterfinals. The next week, on the November 16 edition of "Raw", he defeated Neville at the quarterfinals, advancing to the semifinals. At Survivor Series, Owens was defeated by Dean Ambrose in the semi-finals of the WWE World Heavyweight Championship tournament. On the November 23 episode of Raw, Owens and Tyler Breeze faced Dean Ambrose & Dolph Ziggler in a losing effort.
After Dean Ambrose became the number one contender to the Intercontinental Championship, Owens lost the title to him at TLC on December 13. At the December 28 episode of Raw, Owens debuted a more aggressive persona, as he brutally assaulted Neville after losing to him in seconds, until he was stopped by Ambrose. Later that night, Owens assaulted Ambrose after his match and powerbombed him through the announce table, while Michael Cole called Owens a "madman".
At the 2016 Royal Rumble, Ambrose defeated Owens in a Last Man Standing rematch for the Intercontinental Championship. Owens went on to enter the Royal Rumble match as the 18th entrant with the WWE World Heavyweight Championship on the line and eliminated the debuting AJ Styles. Owens was eventually eliminated by his long time rival, Sami Zayn. The following night on Raw, Kevin Owens faced off against Dolph Ziggler in a winning effort. The following week Owens faced Ziggler again, this time losing to him by pinfall. On the February 4 edition of Smackdown Owens lost to United States Champion Kalisto after a distraction from Ziggler in retaliation for powerbombing Kalisto onto him. On February 8 episode of Raw Owens lost to Ziggler by pinfall again while Ziggler's feet were on the ropes. On the February 15 edition of Raw, Owens pinned Tyler Breeze is a fatal-5-way match involving Stardust, Dean Ambrose, and Dolph Ziggler to become a two-time Intercontinental Champion. It was announced later on in the night that Owens' first title defense will be at Fastlane against Ziggler. Owens would retain the title at Fastlane. In March, it was announced that Owens would defend the Intercontinental Championship in a ladder match against Sami Zayn, Dolph Ziggler, The Miz, Stardust, Sin Cara and Zack Ryder at WrestleMania 32. Owens would lose the title when Ryder won the match.
The night after WrestleMania on Raw, Owens faced AJ Styles, Chris Jericho, and the returning Cesaro in a fatal four-way match to determine the #1 contender for Roman Reigns' newly won WWE World Heavyweight Championship. However, Owens would lose the match when Styles pinned Jericho. He resumed the feud with longtime rival Sami Zayn after he attacked him on Raw. Next week Shane McMahon announced that they would face off at Payback. Owens got the last laugh after attacking Zayn after he won a match against Rusev. At Payback Owens defeated Zayn via pinfall, before announcing his intentions of regaining the WWE Intercontinental Championship, where he proceeded to watch the proceeding match for the title between Miz and Cesaro, where Zayn would attack him once again, leading to The Miz retaining the title against Cesaro, and attacking both men and standing tall with the championship belt in his hands, signifying a future title shot. On May 22 at the Extreme Rules pay-per-view, Owens wrestled in a Fatal Four Way for the Intercontinental Championship, but the match was won by The Miz. The following night on Raw, Owens defeated AJ Styles to qualify for the 2016 Money in the Bank ladder match, but he failed to win the match. At Battleground 2016, Kevin Owens was defeated by Sami Zayn. At SummerSlam, Owens teamed with Chris Jericho to defeat Enzo Amore and Big Cass.
On the August 22 episode of Raw, Owens defeated Neville to qualify for the WWE Universal Championship Fatal-4 Way match the following week. On August 29, Owens defeated Big Cass, Roman Reigns, and Seth Rollins with interference from Triple H to become the new Universal Champion, aligning himself with Triple H. Owens defended the championship against Rollins at the Clash of Champions pay-per-view, which he won after interference from Chris Jericho. On the September 26 episode of Raw, Owens and Chris Jericho defeated Enzo Amore and Big Cass. On the October 3 episode of Raw, Owens and Jericho challenged The New Day for the WWE Raw Tag Team Championships, but lost when Rollins interfered and cost them the match. On the October 24 episode of Raw, Owens competed in a triple treat match against Jericho and Rollins but lost when Rollins pinned both men. After the match, Owens powerbombed Rollins on the ring apron. At Hell in a Cell, Owens defeated Rollins in a Hell in a Cell match to successfully defend the Universal title. Owens and Jericho were later announced as co-captains of Team RAW for the Traditional 5-on-5 Survivor Series inter-promotional elimination tag team match against Team SmackDown Live, alongside Reigns, Rollins and Braun Strowman. Owens was eliminated via disqualification for using "The List of Jericho" as a weapon to attack AJ Styles, subsequently showing tension between Jericho and Owens. Team Raw would later go on to lose the match. After Owens defeated Rollins in a no disqualification match to retain the championship, once again following the interference of Jericho, United States Champion Reigns issued a challenge to Owens, who stated he did not need Jericho's help against him, and Owens suffered his first pinfall loss since becoming champion after losing a non-title match to Reigns that same night, thus earning Reigns a WWE Universal Championship match against Owens at Roadblock: End of the Line on December 18. At Roadblock, Owens first interfered in the match between Jericho and Rollins and tried to help Jericho but failed as Rollins won the match. During his title defense against Reigns, Jericho attacked Owens with a Code-Breaker on purpose to give Owens a victory by disqualification and another successful title defense. They both reunited after which they both were attacked by Rollins and Reigns post match. On December 19 episode of Raw, it was announced that Reigns would get his rematch against Owens at Royal Rumble in which Jericho would be suspended above the ring in a shark cage.