On June 13, 2016, Alexander was announced as a participant in WWE's upcoming Cruiserweight Classic tournament. The tournament began on June 23 with Alexander defeating Clement Petiot in his first round match. On July 14, Alexander was eliminated from the tournament by Kota Ibushi.
On the August 29 episode of Raw, Alexander was announced as part of upcoming cruiserweight division. Alexander made his debut on the September 19 episode of Raw, submitting to Brian Kendrick in a fatal four-may match that included Gran Metalik and Rich Swann to determine the number one contender for the WWE Cruiserweight Championship. On the September 26 episode of Raw, he along with Rich Swann, defeated Lince Dorado and Drew Gulak. On the December 6 episode of 205 Live, it was revealed that Alexander was dating Alicia Fox in storyline, and later faced Noam Dar in a losing effort. After the match, Dar dedicated his victory to Fox, igniting a feud between the two. On the December 19 episode of Raw, Alexander defeated Dar. Alexander later decided to break-up with Fox, after she cost him a match. In late February, it was announced that Alexander would be out of action for 3–5 months with a knee injury. He returned from injury on the May 23 on 205 Live. On the July 11 episode of 205 Live, Alexander defeated Dar in an "I Quit" match to end their feud.
On the December 11 episode of Raw, Alexander won a fatal four-way match, earning a match against Drew Gulak for the number one contendership to the Cruiserweight Championship. Alexander defeated Gulak on December 18, and faced Enzo Amore for the title on January 9, 2018, which Amore lost by countout, therefore retaining. Alexander was scheduled to face Amore for the Cruiserweight Championship at the Royal Rumble pay-per-view, but the match was cancelled and the title was vacated when Amore was released from WWE.
A tournament to determine a new champion was arranged, in which Alexander defeated Gran Metalik in the first round, TJP in the quarterfinals, and Roderick Strong in the semi-finals to advance to the final. At WrestleMania 34 kickoff, Alexander defeated Mustafa Ali to win the Cruiserweight Championship. On the following episode of 205 Live, Alexander was attacked by Buddy Murphy during his championship celebration. On April 27, Alexander made his first successful title defense against Kalisto at the Greatest Royal Rumble. On the May 29 episode of 205 Live, he defeated Buddy Murphy to retain the Cruiserweight Championship. At SummerSlam, Alexander successfully defended his title against Drew Gulak. On the September 19 episode of 205 Live, Alexander defeated Gulak in a SummerSlam rematch to retain the Cruiserweight Championship.
At Super Show-Down, Alexander lost the Cruiserweight Championship against Buddy Murphy, ending his reign at 181 days, also marking his first televised loss in 2018. On the following episode of 205 Live, Alexander lost to Murphy's ally, Tony Nese. The following week on 205 Live, Alexander was pinned by Nese again in a fatal five-way match also involving Gran Metalik, Lio Rush, and TJP.
On the November 14 episode of 205 Live, Alexander defeated Rush to give Rush his first televised loss on 205 Live. Two weeks later on the November 28 episode of 205 Live, Alexander teamed with Mustafa Ali to defeat Murphy and Nese after Alexander pinned Murphy. Alexander received his title rematch against Buddy Murphy at TLC but failed to regain the title. In early 2019, Alexander competed in a tournament for a match for the title at WrestleMania 35. Alexander lasted until the finals of the tournament where he lost to Tony Nese. Alexander later started a feud with Oney Lorcan. On the March 26 episode of 205 Live, he lost the match to Ariya Daivari when Lorcan cost his match.
During the 2019 WWE Superstar Shake-up, Alexander was drafted to Raw. Alexander lost his final match on the April 17 episode of 205 Live against Oney Lorcan. After the match, the two shook hands as a sign of respect, thus ending their feud. On the April 22 edition of Raw, Alexander would lose his debut match against Cesaro. Following that, he rarely appeared on Raw over the next two months, instead wrestling on WWE Main Event. On the June 24 edition of Raw, Alexander briefly won the 24/7 Championship from R-Truth before immediately losing it against EC3 during a flurry of title changes. A couple of weeks later on Raw, Alexander, disguised as "Gary Garbutt", a backstage janitor, teamed with Roman Reigns in a losing effort against Drew McIntyre and Shane McMahon. A week later, Alexander scored an upset victory over McIntyre in a singles match starting a brief feud between the two. On the August 12 episode of Raw, McIntyre defeated Alexander. Alexander then entered the King of the Ring tournament where he defeated Sami Zayn in the first round. The next week, Alexander was attacked backstage by The O.C., causing him to (kayfabe) injure his knee. This would lead to him losing to Baron Corbin later that night, thus ending his chances at becoming King of the Ring. At Clash of Champions, Alexander unsuccessfully challenged AJ Styles for his United States Championship. The following week on Raw, he would attack AJ Styles who was ringside during the match between The Viking Raiders and The O.C., chasing him out of the arena. On the September 30th episode of Raw, Alexander would once again challenge Styles for the United States Championship in a losing effort.
After being off of television and primarily wrestling on Main Event for several months, Alexander would form a tag team with Ricochet on the April 6, 2020 episode of Raw as they defeated Oney Lorcan and Danny Burch. The following week on Raw, they faced The Viking Raiders in a losing effort. In the following weeks, Alexander and Ricochet began feuding with The Hurt Business (MVP, Bobby Lashley, and Shelton Benjamin) after they injured Apollo Crews. On the July 6 episode of Raw, after Alexander and Ricochet lost to MVP and Lashley, MVP approached Alexander and attempted to convince him to join his group with Lashley rather than just be Ricochet's "side kick". On the September 7 episode of Raw, Alexander attacked his tag team partners Ricochet and Apollo Crews during a six-man tag team match against The Hurt Business, thus joining The Hurt Business and turning heel for the first time in his WWE career. Alexander began teaming with Benjamin as they feuded with The New Day (Kofi Kingston and Xavier Woods) for the WWE Raw Tag Team Championship. At TLC, Alexander and Benjamin defeated the New Day to win the WWE Raw Tag Team Championship. They would lose the titles back to The New Day on the March 15, 2021 episode of Raw.\
On the March 29 episode of Raw, Lashley lambasted Alexander and Benjamin due to them losing the Raw Tag Team Championships and losing to Drew McIntyre in a 2-on-1 handicap match, effectively barring them from Lashley's WWE Championship match at WrestleMania 37 against McIntyre. This led to Lashley attacking Alexander and Benjamin, kicking them out of the faction in the process. On the April 5 episode of Raw, Alexander lost to Lashley in singles competition. In the following weeks, Alexander and Benjamin began a losing streak against teams such as The Viking Raiders (Erik and Ivar) twice, and to Riddle and Randy Orton once. On the May 3 episode of Raw, after losing to Lucha House Party (Gran Metalik and Lince Dorado), Alexander insulted Benjamin and said that the team was done.
On the September 27 episode of Raw, Alexander and Benjamin helped Lashley fight off The New Day, in the process reuniting The Hurt Business. On the November 22 episode of Raw, Alexander defeated Reggie to win the 24/7 Championship for a third time, only to lose it to Dana Brooke moments later. Months later in January 2022, after not being seen together, Benjamin and Alexander approached Lashley under the assumption they were still a unit, only to be dismissed. This would cause the pair to launch a sneak attack that evening, but they were easily dealt with.
After his tag team partner Shelton Benjamin became injured, Alexander would be involved in segments where he tried to get in on MVP and Omos' good side during their feud with Bobby Lashley, up until Hell in a Cell, when Alexander distracted MVP and Omos during their two-on-one handicap match, which allowed Lashley to pick up the victory. Later on, Lashley would confront Alexander backstage, questioning his motive behind the involvement, with Alexander saying that the distraction was for himself, therefore turning Alexander face for the first time in two years. On August 8, Alexander defeated Benjamin during Main Event, effectively signaling the end of The Hurt Business.
On the January 9, 2023 episode of Raw, Alexander and Benjamin reunited to take part in a tag team turmoil match. Earlier during the show, Lashley and MVP teased an alliance, with MVP crediting himself for reuniting Benjamin and Alexander, and getting Lashley reinstated on Raw after being suspended. On the February 6 edition of Raw, Alexander and Benjamin defeated Alpha Academy (Chad Gable and Otis) with MVP in their corner, further hinting at a possible reunion. The storyline was then abruptly dropped, however. The partnership would officially end between Alexander and Benjamin after the latter was released from his WWE contract on September 21. On the October 2 Raw, Alexander made his return to television after several months, losing to Bronson Reed in a squash. Alexander then appeared on the October 27 episode of SmackDown, where he was defeated by Dragon Lee. Two weeks later, Alexander lost to Lee once again on SmackDown.
On the February 9, 2024 episode of SmackDown, Alexander was paired with Ashante "Thee" Adonis as a tag team. On the July 9 episode of NXT, Alexander and Adonis joined the NXT brand. In his NXT debut match on the July 23 episode, Alexander was defeated by Trick Williams. At NXT Great American Bash, Alexander would successfully defeat Brooks Jensen.