In April 2017, it was reported that Nox had signed a contract with WWE.
It was reported that Nox was replaced in the Mae Young Classic, because of tearing to her ACL before the tournament had even began. Nox returned to the ring on April 13, 2018, at an NXT live event, where she teamed up with Dakota Kai in a tag team match to defeat Reina González and Vanessa Borne. After being announced as a competitor in the 2018 Mae Young Classic, Newell entered the tournament on August 8, defeating Zatara. Nox returned the following day, defeating Nicole Matthews in the second round, before suffering another knee injury in her quarter-final match against Rhea Ripley. After the match premiered on the WWE Network, Nox posted on Twitter that she had suffered numerous injuries during the match, including: a torn Anterior cruciate ligament, Medial collateral ligament, Lateral collateral ligament, meniscus, and Patellar dislocation.
On June 25, 2019, Nox made her in-ring return at a WWE NXT live event in Orlando, Florida. On September 11, 2019, Nox made her NXT UK debut when she defeated Shax. Afterwards, Nox began a feud with NXT UK Women's Champion Kay Lee Ray, resulting in a championship between the two on the October 2 episode of NXT UK, where Nox was unsuccessful. On October 16, Nox returned to NXT, defeating Taynara. Thereafter, Nox began teaming with long-time friend Dakota Kai, with the two defeating Jessamyn Duke and Marina Shafir to become number one contenders to the WWE Women's Tag Team Championship on the October 23 episode of NXT. Nox and Kai would go on to lose the match against Asuka and Kairi Sane on the October 30 episode of NXT. Two days later on SmackDown, Nox and Ripley were one of the many NXT wrestlers to invade the show, challenging Mandy Rose and Sonya Deville to a tag-team match, which Nox and Ripley emerged victorious. Later that night, Nox joined Triple H and the rest of the NXT roster as they declared war on both Raw and SmackDown, and vowed to win the Survivor Series brand warfare. Nox was chosen by Ripley to join her team as part of a WarGames match at NXT TakeOver: WarGames. At the event on November 23, Ripley's team would go onto win, however Nox would not take part in the match after being attacked by Kai, her teammate. After a short hiatus due to a storyline injury, Nox returned on the January 15, 2020 episode of NXT, competing in a number one contendership battle royal, where she was unsuccessful after Kai interfered. On the January 29 episode of NXT, Nox defeated Kai due to outside interference by Candice LeRae. Nox would lose to Kai in a street fight at NXT TakeOver: Portland after interference by Raquel Gonzalez. On the March 4 episode of NXT, Nox lost to Kai again in a steel cage match, after Raquel González trapped her in the cage door and allowed Kai to escape from the cage. On June 7 at NXT TakeOver: In Your House, Nox teamed up with Mia Yim and Shotzi Blackheart and defeated Dakota Kai, Raquel González and Candice LeRae in a 6-woman tag team match. On the July 1 episode of NXT The Great American Bash, Nox defeated Kai, LeRae and Yim in a number one contender's fatal four-way elimination match, thus earning herself number one contendership for the NXT Women's Championship. On the July 15 episode of NXT, Nox was unsuccessful in her title match against defending champion Io Shirai. On the September 23 episode of NXT, LeRae viciously attacked her with a steel pipe and LeRae ran a crate into her surgically repaired left knee. Nox screamed in pain and was then unable to compete in a NXT Women’s Championship number one contender’s battle royal. On September 30, WWE announced that Nox had once again suffered a torn ACL and would be out of action for an indefinite amount of time.
After a near ten-month absence, Nox returned on July 6, 2021 at The Great American Bash, causing LeRae and Indi Hartwell to lose the NXT Women's Tag Team Championship to Io Shirai and Zoey Stark. After the match, Nox attacked LeRae.
On the July 9 episode of SmackDown, Nox made her main roster debut teaming with Shotzi to defeat the WWE Women's Tag Team Champions Natalya and Tamina in a non-title match. The two would then go on to defeat Natalya and Tamina in numerous tag team matches, but would never receive a championship match. On the October 4 episode of Raw, Nox was drafted to the Raw brand, thus seperating her from Shotzi, who remained on SmackDown. On November 18, she was released from her WWE contract without ever appearing on Raw.
On the December 2, 2022 episode of SmackDown, Nox made her return to WWE, rescuing Liv Morgan from an attack by Damage Control. The following week on the December 9 episode of SmackDown, Tegan Nox and Liv Morgan defeated Ronda Rousey and Shayna Baszler in a tag team match, earning them a shot at the WWE Women's Tag Team Championship. On the December 16 episode of SmackDown, Nox and Morgan lost to Damage Control due to the interference of a masked stagehand, later revealed to be Xia Li. Nox was drafted to the Raw brand in the 2023 Draft. On the September 25 episode of Raw, Nox picked up a victory over Natalya to receive an NXT Women’s Championship match against Becky Lynch. Two weeks later on Raw, Nox unsuccessfully challenged Lynch for the title. In the weeks that follow, Nox would form an alliance with Natalya. This alliance would result in Nox defeating both Women’s Tag Team Champions Chelsea Green and Piper Niven in singles matches. On the November 20 episode of Raw, Nox and Natalya won a fatal four-way tag team match to receive a Women’s Tag Team Championship opportunity. The following week on Raw, Nox and Natalya would challenge for the titles in a losing effort. On January 27, 2024, at the Royal Rumble, Nox entered in her third women’s Royal Rumble match at number twelve. During the match, she was able to eliminate Natalya after Natalya attempted to eliminate her, only to be immediately eliminated herself by Bayley. During the 2024 WWE Draft, Nox was drafted back to the SmackDown brand. However, on November 1, Nox was released from WWE for a second time before ever making her debut on the brand.