On December 2, 2020, Lee signed a contract with WWE and was assigned to the WWE Performance Center. On the January 13, 2021 episode of NXT, Lee and his tag team partner Nash Carter debuted under the team name MSK. They defeated Jake Atlas and Isaiah "Swerve" Scott in the first round of the Dusty Rhodes Tag Team Classic tournament, which they eventually won. At NXT TakeOver: Stand and Deliver, MSK defeated Grizzled Young Veterans and Legado del Fantasma in a triple threat match for the NXT Tag Team Championship. At NXT TakeOver: In Your House, MSK teamed with NXT North American Champion Bronson Reed to defeat Lagado del Fantasma in a winner takes all match, which MSK won. At The Great American Bash event, MSK defeated Tommaso Ciampa and Timothy Thatcher to retain the tag team titles. Over the next two months, MSK defended their titles against Imperium and Oney Lorcan and Danny Burch. At Halloween Havoc, Imperium defeated MSK in a lumberjack match to win the titles. MSK would win the titles for a second time at NXT Stand and Deliver on April 2, 2022, after defeating Imperium in a triple threat tag team match also involving the Creed Brothers. However, on April 6, Carter was released from the company, thus disbanding MSK and vacating the NXT Tag Team Championships.
On the April 19 episode of NXT, Lee returned to television, vaguely addressing the vacating of the tag titles, before being confronted by Xyon Quinn. This led to a match between Quinn and Lee later in the evening, with Lee losing. On the May 24 episode of NXT 2.0, he lost against Sanga, and was taunted by Quinn before Sanga pulled him away. The following week, Lee challenged Quinn to a match and won. On the June 14 episode of NXT 2.0, Wes Lee had another match against Xyon Quinn, which he also won. On the July 5 episode of NXT 2.0, Lee faced Trick Williams with NXT North American Champion Carmelo Hayes in the latter's corner at NXT The Great American Bash, but was not successful due to outside interference. On the August 9 episode of NXT 2.0, Lee would once again face Trick Williams, but this time in a rounds match, where Lee would defeat Williams two rounds to one.
On October 22 at NXT Halloween Havoc, Wes Lee won the vacant NXT North American Championship in a five-man ladder match involving Carmelo Hayes, Von Wagner, Oro Mansah and Nathan Frazer. On the November 1 episode of NXT, NXT Tag Team Champions Pretty Deadly interrupted NXT Champion Bron Breakker. This led to Lee coming out, where he and Breakker challenged Pretty Deadly to a match for their tag team championships later in the show; Lee and Breakker were unsuccessful after Carmelo Hayes interfered.
On the April 18, 2023 episode of NXT, Wes Lee successfully retained the title against Charlie Dempsey. At NXT Stand and Deliver, Lee defended the title in a fatal five-way match against Axiom, Dragon Lee, Ilja Dragunov, and JD McDonagh. At NXT Battleground, Lee retained the North American Championship against Tyler Bate and Joe Gacy. On the July 18 episode of NXT, Lee lost the NXT North American Championship to Dominik Mysterio after interference from The Judgment Day, ending his reign at a record 269 days. Lee failed to regain the NXT North American Championship in a triple threat match against Mysterio and Mustafa Ali at NXT The Great American Bash after another interference from The Judgment Day's Rhea Ripley.
On the August 15 episode of NXT, Lee defeated Dijak to become the number one contender for the NXT Championship, with Lee challenging Carmelo Hayes for the title at NXT Heatwave in a losing effort. On the September 12 episode of NXT, Lee lost to Ilja Dragunov in a number one contender's match for the NXT Championship. Lee quietly returned from a short hiatus on the November 2 episode of Main Event and later appeared on the following night's NXT Halloween Havoc to attack Dominik Mysterio after Mysterio's NXT North American Championship match against Nathan Frazer. On the November 28 episode of NXT, Lee defeated three former NXT North American Champions in Cameron Grimes, Bronson Reed and Johnny Gargano in a fatal-four way match as demanded by Mysterio the week before for a title match against Mysterio at NXT Deadline. However, a week later, Lee revealed he would need back surgery and be out of action for eight to twelve months, with Dragon Lee replacing him in the match at Deadline.
During week two of Spring Breakin' on April 30, 2024, Lee made a surprise return from injury and confronted NXT North American Champion Oba Femi after his title match against Ivar. Lee defeated Josh Briggs in his first match since the injury on the following week's episode of NXT. On the May 21 episode of NXT, Lee and Joe Coffey both pinned Briggs, and the two men were considered the winner. Later that night, NXT General Manager Ava set up a triple threat match between Lee, Femi and Coffey for the title at NXT Battleground. At the event, Lee was unsuccessful in winning the title. On the June 16 episode of NXT, Lee again requested for a title match against Femi. Femi agreed under the stipulation that Lee could never challenge Femi for the title for as long as he was champion if Lee lost. At NXT Heatwave on July 7, Femi defeated Lee to retain the title. On the following episode of NXT, Lee was about to announce that he would walk away from NXT, but was interrupted by Trey Miguel and former MSK teammate Nash Carter, now going by the name Zachary Wentz, who managed to convince Lee to stay. The following week, MSK defeated Gallus (Joe Coffey, Mark Coffey, and Wolfgang) in a six-man tag team match. During week two of The Great American Bash on August 6, Wentz and Lee failed to defeat NXT Tag Team Champions Nathan Frazer and Axiom for the titles. After the match, Lee turned on Miguel and Wentz, lashing out at the latter for leaving him back in 2022 and turning heel for the first time in his career, leaving MSK in the process. On the August 20 episode of NXT, Lee faced Pete Dunne and Joe Hendry in a triple threat match for an NXT Championship opportunity at NXT No Mercy, which was won by Hendry. After the match, Lee was attacked by Wentz.