In June 2013, Carmella signed a contract with WWE and she was assigned to the company's developmental territory NXT in late September.
Carmella made her debut on the September 4, 2014 episode of NXT, portraying a hairdresser in a segment with Enzo Amore and Colin Cassady. Two weeks later on NXT, Carmella appeared in another segment with Amore and Cassady at the WWE Performance Center, announcing she had lost her job as a hairdresser due to Amore and Cassady's actions and asked for a job at NXT. She made her in-ring debut on the October 16 episode of NXT, wrestling an unnamed opponent whom Amore and Cassady dubbed Blue Pants. Carmella defeated Blue Pants on two occasions, but lost to her on the January 1, 2015 episode of NXT after Amore accidentally caused a distraction. In March, Amore and Cassady began a rivalry with the NXT Tag Team Champions Blake and Murphy while Carmella rejected Blake and Murphy's advances on several occasions. On the May 13 episode of NXT, Carmella was defeated by Alexa Bliss after a distraction by Blake and Murphy. On May 20 at NXT TakeOver: Unstoppable, Bliss attacked Carmella during the NXT Tag Team Championship title match, ensuring the win for Blake and Murphy.
While continuing to manage Amore and Cassady, Carmella began feuding with Eva Marie, which led to a match between the two on the August 26 episode of NXT, which Carmella lost. In January 2016, Carmella won a battle royal to become the number one contender to Bayley's NXT Women's Championship. Carmella unsuccessfully challenged Bayley for the title on February 10. After the match, Eva Marie and Nia Jax attacked the two, which led to a tag team match on the February 24 episode of NXT, which Carmella and Bayley lost. Carmella made her first appearance on WWE's main roster on March 12 at Roadblock, accompanying Amore and Cassady for their match against The Revival for the NXT Tag Team Championship. On the May 25 episode of NXT, Carmella competed in a triple threat match against Alexa Bliss and Nia Jax to determine the number one contender to Asuka's NXT Women's Championship at NXT TakeOver: The End, but she was pinned by Jax.
After being drafted to the SmackDown brand on July 19 as part of the 2016 WWE draft, Carmella made her main roster debut for the brand a week later, confronting the brand female talents before being interrupted by Eva Marie. On the August 9 episode of SmackDown Live, Carmella achieved her first victory on the main roster by defeating Natalya. On August 20 at SummerSlam, Carmella took part in a six-woman tag team match alongside Becky Lynch and Naomi that was won by their opponents Alexa Bliss, Natalya, and Nikki Bella after Bella pinned Carmella. Two days later on SmackDown Live, Carmella attacked Nikki Bella, turning heel in the process and starting a storyline feud between the two. Simultaneously with her feud with Bella, Carmella took part in a six-pack elimination challenge to determine the inaugural SmackDown Women's Champion on September 11 at Backlash. She was the last woman eliminated by Becky Lynch. She was also part of Team SmackDown in the traditional five-on-five Survivor Series match on November 20 at Survivor Series against Team Raw, where she was the first participant eliminated by Alicia Fox. On December 4 at TLC: Tables, Ladders & Chairs, Carmella lost to Nikki Bella in a no disqualification match to end their feud.
Carmella then moved into a storyline with James Ellsworth, professing that she found him "uniquely attractive" and he later started accompanying her to her matches. On April 2, 2017, Carmella made her WrestleMania debut at WrestleMania 33, competing in a six-pack challenge for the SmackDown Women's Championship, but was unsuccessful. In late April, Carmella formed an alliance, dubbed The Welcoming Committee, with Natalya and Tamina, and the three started a feud with Becky Lynch, Charlotte Flair, and Naomi. The two teams faced off in a six-woman tag team match on May 21 at Backlash, where The Welcoming Committee was victorious.
On June 18 at Money in the Bank, Carmella was declared the winner of the inaugural women's Money in the Bank ladder match after Ellsworth obtained the briefcase and dropped it to her. Two days later on SmackDown, Carmella was stripped of the briefcase and a second Money in the Bank ladder match was set by SmackDown General Manager Daniel Bryan. On June 27, Carmella regained the Money in the Bank briefcase after she won the second match with the help of Ellsworth. In November, Carmella ended her association with Ellsworth after he lost to Becky Lynch in an intergender match. On January 28, 2018, at the Royal Rumble, Carmella participated in the first women's Royal Rumble match, where she entered at number seventeen, lasting over 18 minutes before being eliminated by her former rival Nikki Bella. She then appeared in the first WrestleMania Women's Battle Royal at WrestleMania 34, but was the first woman eliminated from the match by Sonya Deville.
After 287 days (the longest period ever for a wrestler to hold the contract) and a few unsuccessful attempts to cash in her briefcase on Charlotte Flair, Carmella officially cashed in her contract on the April 10 episode of SmackDown Live, after The IIconics (Billie Kay and Peyton Royce) attacked Charlotte Flair, she defeated Flair to win the SmackDown Women's Championship for the first time in her career. In her first title defense, Carmella defeated Charlotte Flair at Backlash. Shortly after, Carmella was placed in a feud with Asuka that ultimately led to a title match between the two at Money in the Bank, which Carmella won after a distraction by the returning James Ellsworth. In a rematch between the two, which took place at Extreme Rules, Carmella again defeated Asuka to retain her title (with Ellsworth suspended in a shark cage). After losing to both Becky Lynch and Charlotte Flair in non–title matches, it was announced that Carmella would face both in a triple threat match at SummerSlam on August 19. At the event, Flair pinned Lynch to win the championship, ending Carmella's reign at 131 days. Two weeks later, Carmella received her rematch against Flair but she was unsuccessful in regaining the title.
Towards the end of her title reign, Carmella was placed in a storyline with R-Truth, after the latter implied that he wants a "title match by pinning her" (similar to Becky Lynch and Charlotte Flair's title opportunities). On the September 4 episode of SmackDown Live, Carmella turned face for the first time since 2016, after she agreed to manage Truth for his match with The Miz to avoid Maryse's interference. Shortly after, Carmella started managing Truth and the two were also announced as tag team partners for the upcoming season two of Mixed Match Challenge. In November, Carmella once again took part of Survivor Series as part Team SmackDown, where she went on to eliminate Tamina before being eliminated by Bayley. Carmella and Truth lost the first three matches of Mixed Match Challenge before defeating Rusev and Lana to qualify for the playoffs. The team went on to defeat Jeff Hardy and Charlotte Flair in the quarter–finals and previous winners The Miz and Asuka in the semi–finals. In the final of the Mixed Match Challenge that took place at the TLC: Tables, Ladders & Chairs pay–per–view, on December 16, Carmella and Truth defeated Jinder Mahal and Alicia Fox, earning both the number 30 spots for their respective Royal Rumble matches at the Royal Rumble.
In January 2019, Carmella competed in a triple threat match to determine the number one contender for the SmackDown Women's Championship, however, Becky Lynch won the match by submitting her. At the Royal Rumble, Carmella lasted 7 minutes and scored an elimination, but she was unsuccessful in winning the match as she was eliminated by Flair. In February, Carmella started teaming up with Naomi and the two took part of a six–team Elimination Chamber match for the inaugural WWE Women's Tag Team Championship at the namesake pay–per–view, where they were the first team eliminated. On April 6, at WrestleMania 35, Carmella won the second WrestleMania Women's Battle Royal by lastly eliminating Sarah Logan. In May, Carmella took part in the Money in the Bank ladder match at the namesake pay–per–view, where she once again displayed a knee injury and was ultimately unsuccessful in winning the match. The "knee injury" was used to spark a feud between Carmella and both Mandy Rose and Sonya Deville. In parallel to her feud with Rose and Deville, Carmella continued to manage R-Truth, who won the WWE 24/7 Championship and she helped him escape and defend it against various competitors. On the September 23 episode of Raw, Carmella rolled–up Truth to capture the 24/7 Championship from him. Her title reign came to an end 11 days later, during SmackDown's 20th Anniversary on October 4, when she was pinned by Marshmello backstage. Later that night, Carmella regained the title from Marshmello in a segment that took place in the parking lot. On October 6, during the Hell in a Cell event, Tamina pinned Carmella to end her second reign with the title at only 2 days. A few minutes later, Carmella helped R-Truth defeat Tamina to win the 24/7 Championship. The alliance between Carmella and R-Truth was ended abruptly during the 2019 Draft, when Carmella remained on SmackDown and R-Truth was moved to the Raw brand. On the November 8th episode of SmackDown, Carmella and Dana Brooke defeated Fire and Desire (Mandy Rose and Sonya Deville) to qualify for the SmackDown women's team for the Survivor Series Elimination Match, which her team went on to lose. Carmella participated in the Royal Rumble match at the namesake pay-per-view and entered at number twenty-seven, but was eliminated by Shayna Baszler. On the April 24 episode of SmackDown, Carmella and Dana Brooke unsuccessfully challenged Alexa Bliss and Nikki Cross in a title match for the Women's Tag Team Championships. On the May 1 episode of SmackDown, Carmella defeated Mandy Rose to qualify for the Money in the Bank ladder match. At Money in the Bank, Carmella failed to win the match.
On the October 2 episode of SmackDown, Carmella made her return as she revealed herself as SmackDown's mystery woman, whose debut had been teased in the weeks prior, while also going by the new mantra of "Untouchable", thus turning heel once again. On the November 6 episode of SmackDown, Carmella attacked the SmackDown Women's Champion Sasha Banks from behind following Banks' successful title defense against Bayley. Towards the end of the year, the two continued to cut promos and attack each other, which eventually led to a match for the SmackDown Women's Championship at the TLC: Tables, Ladders & Chairs event. At the event, on December 20, Carmella faced Banks for the title in a losing effort.
Carmella would team up with Billie Kay at WrestleMania 37 to participate in a tag team turmoil match to determine the number one contenders against Nia Jax and Shayna Baszler for the WWE Women's Tag Team Championship, but were unsuccessful in the match. Carmella then faced both members of the Riott Squad individually, and beat them both. She would then have three opportunities for the SmackDown Women’s Championship against Bianca Belair, one on the July 16 episode of SmackDown, one on the July 23 episode, and one at a house show in Louisville, Kentucky, but all three of them would prove unsuccessful. Carmella was then scheduled to be Sasha Banks' replacement for SummerSlam against Bianca Belair, but was then attacked by a returning Becky Lynch. Carmella lost to Liv Morgan on the Extreme Rules kickoff show.
As part of the 2021 Draft, Carmella was drafted to the Raw brand. In October, Carmella entered the Queen's Crown tournament, where she defeated Liv Morgan in the first round, but lost to Zelina Vega in the semifinals. Also during this time, Carmella began using a protective face mask to shield her face from attacks. On the November 22 episode of Raw, Carmella and Queen Zelina defeated Rhea Ripley and Nikki A.S.H. to win the WWE Women's Tag Team Championship. On night two of WrestleMania 38, Queen Zelina and Carmella lost the titles to Sasha Banks and Naomi in a fatal four-way tag match, which also included the team of Shayna Baszler and Natalya, as well as the team of Rhea Ripley and Liv Morgan. The following night on Raw, Queen Zelina would blame Carmella for their loss at WrestleMania 38, which led to Zelina attacking Carmella, thus ending their alliance. Carmella would suffer an injury during a live event on August 6.
Carmella returned on the January 30, 2023 episode of Raw. The following week on Raw, Carmella defeated Candice LeRae, Mia Yim, and Piper Niven in a fatal four-way match to qualify for the women's Elimination Chamber match at the namesake pay-per-view. At the event, Carmella failed to win the match after she was last pinned by Asuka.