On March 31, 2016, Dar was announced as a participant in WWE's upcoming Global Cruiserweight Series tournament. The tournament, now renamed the "Cruiserweight Classic", began on June 23 with Dar defeating Gurv Sihra in his first round match. On July 14, Dar defeated Ho Ho Lun in his second round match. On August 26, Dar was eliminated from the tournament in the quarterfinals by Zack Sabre Jr.. During the Cruiserweight Classic finale, Dar teamed with Cedric Alexander in a losing effort against Tommaso Ciampa and Johnny Gargano.
On the August 22 episode of Raw, Dar was announced as part of the upcoming cruiserweight division and had signed with WWE in the process. On the November 7 episode of Raw, Dar teamed with The Brian Kendrick in a losing effort against Rich Swann and Sin Cara in his main roster debut, which also was in his hometown. On the December 6 episode of WWE 205 Live, Dar was victorious over Cedric Alexander. After the match, Dar cut a villainous promo, establishing himself as a heel in the process.
In early 2017, Dar began an on-screen relationship with Alicia Fox. Fox was previously involved in an on-screen relationship with Alexander. After two separate occasions in which Alexander was defeated by Dar, the two had a third match on the January 10 edition of 205 Live. Fox interfered in the match on behalf of Dar, allowing him to defeat Alexander once again, officially siding with Dar. Dar and Fox would subsequently accompany each other to their respective matches. At Fastlane, Dar teamed with Kendrick in a losing effort against Swann and Akira Tozawa.
After weeks of Fox receiving anonymous flowers (in which Dar would take credit for them), Swann revealed himself to be the sender on the April 18 edition of 205 Live. Fox chose to side with Swann, abandoning Dar. Dar and Fox reunited on the May 2 edition of 205 Live after Dar defeated Swann. The two would team together in a losing effort to Swann and Sasha Banks at Extreme Rules. Dar lost to a recently-returning Alexander on the July 11 edition of 205 Live in an "I Quit" match. Following his loss, Dar broke up with Fox. In the later-half of 2017, Dar joined "The Zo Train," a faction consisting of Ariya Daivari, Drew Gulak, Tony Nese and Cruiserweight Champion Enzo Amore.
On December 12, 2017, it was reported that Dar had suffered a knee injury and that he would require surgery. On the June 20, 2018 tapings for WWE's United Kingdom Championship Tournament, Dar returned to action in a fatal four-way match, defeating Flash Morgan Webster, Mark Andrews and Travis Banks to become the number one contender for the WWE United Kingdom Championship.
On July 3, 2018, Dar made his return to 205 Live, defeating TJP as a face for the first time in his WWE tenure in the process. A week later, Dar had a rematch with TJP, in a losing effort via submission. On his return, he began a brief feud with Lio Rush. Dar was supposed to face Rush on the September 19 of 205 Live, however Rush postponed the match for next week, in which Rush won. Dar began a feud with Tony Nese where Nese attacked him backstage. The feud ended however on the February 12 edition of 205 Live in a no disqualification match, in which Nese won.
On October 17, on the first episode of NXT UK, Dar unsuccessfully challenged Pete Dunne for the WWE United Kingdom Championship in the main event. On the March 13, 2019 episode of NXT UK, Dar turned heel by hating on the cruiserweights in NXT UK; Dar then offered Mark Andrews a handshake, then tried attacking Andrews who countered and sent Dar out of the ring. The following episode featured a match between Andrews and Dar that resulted in a no-contest. During the match, Dar injured his knee which kept him out of action for almost two months. On April 19, he returned from injury at the NXT UK television tapings. At NXT UK TakeOver: Cardiff, Noam Dar defeated Travis Banks in his first TakeOver of any kind. In 2020, it was announced that Dar would be apart of the NXT UK Heritage Cup tournament. He defeated Alexander Wolfe in the first round of the tournament, with Pete Dunne, as the special guest referee. On the November 5 episode of NXT UK, Dar lost to A-Kid in the second round of the Heritage Cup. In 2021, Dar began hosting his own talk show called Supernova Sessions, and began an association Sha Samuels. On the October 7, 2021 episode of NXT UK, Dar beat Wolfgang to become the next number one contender to the NXT UK Heritage Cup. On the October 28 episode of NXT UK, Noam Dar beat Tyler Bate 2-1 to win the NXT Heritage Cup, winning his first championship in WWE in the process.
On the July 14 episode of NXT UK, Dar lost the NXT Heritage Cup Championship to Mark Coffey, with the match ending in the sixth round. Dar would go on to regain the NXT UK Heritage Cup Championship from Coffey on the July 7 tapings of NXT UK. Dar would eventually become the final holder of the NXT UK Heritage Cup, as the NXT UK brand was discontinued on September 1, 2022.
Dar would eventually reappear on the April 4, 2023 episode of NXT. Making his debut for NXT's main brand, Dar appeared to seek a new challenger for his Heritage Cup. Dar then made his NXT in-ring debut on the April 18 episode, defeating Myles Borne in a non-title match. On the May 16 episode of NXT, Dragon Lee challenged Dar to a match at NXT Battleground for the NXT Heritage Cup, which he accepted. At Battleground, Dar would defeat Dragon Lee to retain the Heritage Cup with assistance from Jakara Jackson, Lash Legend and Oro Mensah. On the June 6 edition of NXT, during a backstage segment, Dar would accept Nathan Frazer's challenge for the Heritage Cup and introduce the group as the Meta-Four. The following week, it was revealed that Dar suffered a knee injury, therefore Mensah defended the NXT Heritage Cup on Dar's behalf, but was defeated by Frazer, ending Dar's second reign at 292 days. At NXT Heatwave on August 22, Dar defeated Frazer to win the NXT Heritage Cup for a record-setting third time. On night one of NXT Halloween Havoc, Akira Tozawa returned to NXT and stole the Heritage Cup under The Meta-Four's noses. Tozawa returned the Heritage Cup to Dar on night two before managing to spook Dar into a match for the Cup on the following week's NXT, with Dar winning the match 2-1. On the February 27, 2024 episode of NXT, Dar lost the Heritage Cup to No Quarter Catch Crew's Charlie Dempsey, losing the match 2-1 and ending his third reign at 189 days. On March 26, it was announced that The Meta-Four would be the host of NXT Stand and Deliver. Around this time, Dar would start a rivalry with new NXT Champion Trick Williams. During a Supernova Sessions on the May 7 episode of NXT, Dar said that in a match between them where Williams won, Dar's leg was under the ropes, which should have broken the pinfall, and called Williams a fraud. Dar proceeded to attack Williams shortly after Legend revealed that she was having a relationship with Williams. On the following episode of NXT, Dar was found attacked by an unknown assailant. Later that night, Mensah was defeated by Je'Von Evans after interference from Williams. On the May 28 episode of NXT, a debuting Ethan Page revealed himself as Dar's attacker.