In April 2015, Wolfe began training at the WWE Performance Center as part of a class of 10 international WWE recruits. He made his television debut on 15 July 2015 episode of NXT, losing to Samoa Joe.
In 2016, Wolfe formed a tag-team with Sawyer Fulton at NXT live events. In September, Wolfe and Sawyer joined a stable called Sanity, which also included Eric Young and Nikki Cross. The stable made its debut on the 12 October episode of NXT, with Wolfe and Fulton defeating the team of Bobby Roode and Tye Dillinger as part of the Dusty Rhodes Tag Team Classic. On the 2 November episode of NXT, in the second round of the tournament, Wolfe and Fulton defeated the team of T.J. Perkins and Kota Ibushi. Wolfe and Fulton lost to TM-61 in the semi-finals of the tournament. On 19 August 2017, at NXT TakeOver: Brooklyn III, Wolfe and Eric Young defeated The Authors of Pain to win the NXT Tag Team Championship, becoming the first German to hold a championship in WWE. Young and Killian Dain lost the Tag Team Championship to The Undisputed Era (Bobby Fish and Kyle O'Reilly) on 20 December episode of NXT.
During the 2018 WWE Superstar Shake-up, SAnitY (excluding Cross) were drafted to SmackDown. The group debuted on the 19 June episode of SmackDown Live where they attacked The Usos. The following week, SAnitY lost to The Usos and Jeff Hardy. On the 3 July episode of SmackDown Live, the group attacked The New Day. This led to a tables match between the two teams at Extreme Rules, which SAnitY won. On the 24 July episode of SmackDown Live, SAnitY and The New Day faced off in the first round of the WWE SmackDown Tag Team Championship No. 1 Contender's tournament. SAnitY (represented by Wolfe and Dain) were defeated.
The group competed in only two more televised matches throughout the remainder of 2018, while primarily competing at live events. After a near four month hiatus from television, SAnitY returned on the 2 April 2019 episode of SmackDown Live, losing a three-on-one Falls Count Anywhere match to The Miz. During the 2019 Superstar Shake-up, Young was drafted to Raw, thus disbanding SAnitY.
Following the disbanding of Sanity, Wolfe made his debut appearance for WWE's NXT UK brand during the NXT UK tapings on April 20, 2019, joining the brand and aligning himself with the Imperium faction alongside Walter, Fabian Aichner, and Marcel Barthel. On the July 3 episode of NXT UK, Wolfe made his in-ring debut for the brand, defeating Jack Starz. Wolfe, along with Imperium, appeared on the November 11 episode of Raw, accompanying and interfering during Walter's match against WWE Universal Champion Seth Rollins until Kevin Owens and the Street Profits made the save, leading to an eight-man tag team match, where Imperium were defeated after Rollins pinned Wolfe. Through the end of the year, Imperium began a feud with Ilja Dragunov in NXT UK and with The Undisputed Era on NXT. On the November 12 episode of NXT UK, Wolfe defeated Dragunov; however three weeks later, Dragunov defeated Wolfe in a no disqualification match. At Worlds Collide, Imperium faced the Undisputed Era, and during the match, Wolfe suffered and injury; however Imperium ultimately won the match. On the March 12, 2020 episode of NXT UK, Wolfe was defeated by Finn Bálor. On the May 18, 2021 episode of NXT, after Wolfe was defeated by Killian Dain, he was attacked by Aichner and Barthel, thus kicking him out of the faction. The next day, he was released from his WWE contract.