In December 2012, it was reported that Bayley had signed with WWE. In January 2013, Bayley made her debut for WWE's developmental territory NXT at a live event, wrestling under a mask. She made her NXT television debut in a loss to Paige on the March 20 episode. On June 12, Bayley adopted a new character of a doe-eyed fangirl, then lost to Alicia Fox in the first round of the NXT Women's Championship tournament to crown the inaugural champion. On August 21, Bayley unsuccessfully challenged AJ Lee for the Divas Championship. Bayley got her first win, by teaming with Charlotte against Alicia Fox and Aksana on September 4. To Charlotte's annoyance, The BFFs—Beautiful, Fierce Females (Sasha Banks and Summer Rae), attempted to convince Bayley to join them, but this led to Charlotte attacking Bayley during their match against the BFFs on November 13 and promptly joined the BFFs instead. Bayley then formed a brief alliance with main roster diva Natalya, defeating Sasha Banks in both tag team and singles matches. On May 1, 2014, Bayley failed to advance in a tournament for the vacant NXT Women's Championship after losing to Banks in the first round. After pinning Charlotte in a tag team match, Bayley defeated Sasha Banks to become the number one contender to Charlotte's NXT Women's Championship, but she was unsuccessful in capturing the title at NXT TakeOver: Fatal 4-Way, and in a rematch that took place on October 2. In mid-October, after losing to Banks, Bayley was attacked by her former friend Becky Lynch, who allied with Banks, and Bayley later formed an alliance with former rival Charlotte to feud with Banks and Lynch throughout the following several weeks. On the November 27 episode, Bayley was attacked by Banks and Lynch, injuring her knee in the storyline. She returned on the January 21, 2015, episode, saving Charlotte from an attack by Banks and Lynch, before reluctantly attacking Charlotte herself. On February 11 at NXT TakeOver: Rival, Bayley competed in a fatal four-way match for the NXT Women's Championship, but she failed to capture the title.
In March 2015, Bayley began a feud with Emma after she criticized Bayley for her niceness and claimed that it had prevented her from winning the NXT Women's Championship. This led to a match between the two on the April 1 episode, which Bayley won. On the April 29 episode, Bayley was defeated by Dana Brooke after a distraction by Emma. Bayley gained revenge on Emma the following week, where she attacked her after Emma's loss to Charlotte in a match. At NXT TakeOver: Unstoppable on May 20, Bayley teamed up with Charlotte to defeat Emma and Brooke. On the May 27 episode, Bayley was defeated by Emma, and after the match she and Charlotte were attacked by Emma and Dana Brooke. After a short hiatus, Bayley returned from a broken hand injury, on the July 22 episode, where she defeated Emma and stated she had her sights set on the NXT Women's Championship, officially ending their feud.
In August 2015, after defeating Charlotte, Bayley defeated Becky Lynch to become the new number one contender for the NXT Women's Championship. On August 22 at NXT TakeOver: Brooklyn, Bayley defeated Sasha Banks to win the NXT Women's Championship for the first time, and after the match she celebrated with Banks, Lynch and Charlotte. In a rematch between the two, contested in the main event at NXT TakeOver: Respect on October 7, in the first ever women's 30-minute Iron Man match in WWE history, Bayley defeated Banks with three falls to two after securing the third fall with three seconds left in the match to retain the championship. Throughout her championship reign, Bayley went on to fend off title contenders such as Alexa Bliss, Eva Marie, Nia Jax and Carmella.
On the March 16, 2016 episode of NXT, after Bayley and Asuka won a tag team match, NXT general manager William Regal announced that Bayley would defend her championship against Asuka on April 1 at NXT TakeOver: Dallas. At the event, Bayley lost the championship to Asuka, ending her reign at 223 days. After a brief hiatus from in-ring competition, Bayley returned on the May 18 episode after being challenged by Nia Jax to a match, in which she was defeated. After being replaced by Jax at NXT TakeOver: The End due to a storyline injury which made her unable to compete in a rematch for the NXT Women's Championship against Asuka, Bayley made her return on the June 22 episode, where she defeated Deonna Purrazzo. On the July 27 episode, Bayley asked NXT general manager William Regal for a rematch against Asuka for the NXT Women's Championship at NXT TakeOver: Brooklyn II, which he granted. Two weeks later on the August 10 episode, a contract signing was held between both women, which they accepted and signed. At the event on August 20, Bayley failed to regain the title, in what was her final match in NXT.
On July 24, at Battleground, Bayley made her WWE main roster and pay-per-view debut in a one-off appearance as Sasha Banks' mystery tag team partner, defeating Charlotte and Dana Brooke. On the August 22 episode of Raw, Bayley made her official main roster debut after being established as part of the brand by Raw general manager Mick Foley, where she confronted and challenged the Raw Women's Champion Charlotte to a title match, which Charlotte refused and instead forced protégé Brooke to face her, whom Bayley defeated. At Clash of Champions, Bayley was unsuccessful in winning the championship from Charlotte in a triple threat match, which also included Banks. Throughout this time, she entered a feud with Brooke and the two brawled and traded victories in matches. This culminated in a match at Hell in a Cell on October 30, which Bayley won. At Survivor Series on November 20, Bayley survived alongside Charlotte Flair as members of Team Raw, but as was attacked by Flair after the match.
On January 2, 2017, Bayley defeated Nia Jax to become the number one contender for Flair's Raw Women's Championship. She challenged Flair at the Royal Rumble but was unsuccessful in capturing the title. She earned a rematch after she, Cesaro and Sheamus defeated Flair, Gallows and Anderson the next night on Raw, with Bayley pinning Flair. Two weeks later on the February 13 episode, Bayley defeated Flair in the main event to win the Raw Women's Championship after an assist from Banks. At Fastlane, Bayley retained the title against Charlotte thanks to a distraction from Banks and in turn gave Charlotte her first pay-per-view loss. At WrestleMania 33 in Bayley's WrestleMania debut, she retained the title against Charlotte, Banks and Jax in a fatal four-way elimination match. On April 30, Bayley dropped the title to Alexa Bliss at Payback, ending her reign at 76 days. She failed to regain the title in a kendo stick on a pole match at Extreme Rules on June 4. In July 2017, Bayley again became the number one contender for the championship and was slated to face Bliss at SummerSlam on August 20, but she suffered a separated shoulder injury which left her unable to perform. Bayley returned from her injury on the September 18 episode of Raw to help Banks fend off Bliss and Jax. At No Mercy six days later, she lost a fatal five-way match for the Raw Women's Championship.
On November 19, 2017, at Survivor Series, Bayley was again part of Team Raw in a five–on–five elimination tag team match, from which she was eliminated by Tamina. Towards the end of the year, Bayley, alongside Sasha Banks and Mickie James, started a feud with Absolution (Paige, Mandy Rose and Sonya Deville) that led to various singles and tag team matches, mostly won by Absolution. On January 28, 2018, at the Royal Rumble, Bayley competed in the inaugural women's Royal Rumble match, entering at number 29, but was quickly eliminated by her best friend, Banks. A few weeks later, on February 25 at Elimination Chamber, Bayley took part in the first women's Elimination Chamber match, where she was eliminated by Alexa Bliss after Banks pushed her off a pod.
On the WrestleMania 34 kick-off show, Bayley competed in the inaugural WrestleMania Women's Battle Royal, where she got revenge by eliminating Banks, and was the last woman eliminated from the match by its winner, Naomi. On the March 26 episode of Raw, after weeks of animosity, including Bayley betraying Banks during their matches, Bayley and Banks brawled backstage and had to be separated. The two faced off in mid-April but their match ended in a no-contest after The Riott Squad (Ruby Riott, Sarah Logan, and Liv Morgan) interfered and attacked them both. Throughout mid-2018, Bayley and Banks continued to attack each other, and were told to attend counselor meetings to help maintain their friendship. In July, the two reconciled and created a tag team, known as "The Boss 'n' Hug Connection". On February 17, 2019, at the Elimination Chamber, Bayley and Banks won the inaugural WWE Women's Tag Team Championship by lastly eliminating Mandy Rose and Sonya Deville in a tag team Elimination Chamber match. They successfully defended their tag team titles at Fastlane against Nia Jax and Tamina. At WrestleMania 35 on March 25, 2019, they lost the titles in a Fatal 4-Way match when Bayley was pinned by Billie Kay ending their reign at 49 days.
During the Superstar Shake-up on April 16, 2019, Bayley was drafted to SmackDown, disbanding her team with Sasha Banks, who remained on Raw. At The Shield's Final Chapter, Bayley teamed with Ember Moon to defeat The Riott Squad.
On May 19, 2019, at Money in the Bank, Bayley won the women's Money in the Bank ladder match, granting her a women's championship match at any time of her choosing. Later that night, after Charlotte Flair defeated Becky Lynch to win the SmackDown Women's Championship, Lynch was attacked by Flair and Lacey Evans. Bayley came out to save Lynch and fended off both Flair and Evans. With Flair down, Bayley cashed-in her contract and won the SmackDown Women's Championship for the first time (thus quietly end her frienship and also quietly disbaned her team with Banks). The win made her the first WWE Women's Grand Slam winner in WWE history. Throughout June and early July, Bayley feuded with Alexa Bliss and Nikki Cross where she defeated Bliss once in June at Stomping Grounds and she retained her title over Bliss and Nikki Cross in a Handicap match at Extreme Rules in July.
Bayley then offered to defend the SmackDown Women's Championship against Ember Moon at SummerSlam, Ember accepted her challenge on the July 16 SmackDown Live after they defeated Mandy Rose and Sonya Deville. Bayley successfully defended her title against Moon at SummerSlam. On the September 2 episode of Raw, Bayley teamed with Raw Women's Champion Becky Lynch to face off against WWE Women's Tag Team Champions Alexa Bliss and Nikki Cross in a tag-team match, which they emerged victorious via disqualification after Bayley's former partner, Sasha Banks, interfered and attacked Lynch. When Banks was ready to hit Lynch with a steel chair, Bayley stopped her, before subsequently assaulting Lynch herself with the chair, thus turning heel for the first time in her WWE career. The following night on SmackDown, Bayley justified her assault on Lynch, explaining that she only helped Banks because of their friendship and still proclaimed she was the same person she'd always been and wouldn't change, before being interrupted by Charlotte Flair, whom Bayley was scheduled to defend her title against at Clash of Champions, and the two traded insults until Banks arrived, and they ganged up on Flair before attacking her with a steel chair together. At Clash of Champions, Bayley retained against Flair after pushing her into an exposed turnbuckle. The next month, at Hell in a Cell, Bayley lost the title to Charlotte, ending her reign at 140 days. On the October 11 episode of SmackDown, Bayley debuted a new look, having cut off her ponytail and attacked the inflatable tube men during her entrance. She then regained the title from Charlotte Flair again. After the match, she debuted new entrance music and verbally attacked the fans, solidifying her heel turn.
In the lead-up to Survivor Series, Bayley began feuding with Raw Women's Champion Becky Lynch and NXT Women's Champion Shayna Baszler, leading to a non-title triple threat match between the three at the event. Baszler would pick up the win in what would be the main event of the pay-per-view, after submitting Bayley. Shortly after Survivor Series, she begin a feud with Lacey Evans after verbally insulting the women of the SmackDown roster for their poor performance at Survivor Series. At the Royal Rumble, Bayley successfully retained her title against Evans.
On the February 27, 2020, Bayley made history at Super ShowDown by becoming the first woman to successfully defend a championship in Saudi Arabia against Naomi.
On the March 20 episode of SmackDown, Bayley and Sasha Banks came to the ring saying that they were going to skip WrestleMania 36 this year. They were interrupted by Paige, who announced that Bayley would defend her title against Lacey Evans, Dana Brooke (who was later removed from the match), Tamina, Naomi, and Sasha Banks in a six-pack elimination match at WrestleMania 36. At the event, Bayley accidentally hit Banks, who had been teaming up with Bayley for a majority of the match, causing a short argument between the two. Lacey Evans took advantage of the distraction to eliminate Banks, however Bayley ended up retaining her title after Banks returned to the ring and attacked Lacey Evans. On the April 10 episode of SmackDown, Tamina challenged Bayley to a SmackDown Women's Championship match. Bayley accepted, but only if Tamina could defeat Sasha Banks the following week. Tamina beat Banks on the April 17 episode of SmackDown, and a SmackDown Women's Championship match between the two was scheduled for Money in the Bank. At the event, Bayley retained the title after a distraction from Sasha Banks.
On the June 5 episode of SmackDown (taped May 19), Bayley and Banks defeated Alexa Bliss and Nikki Cross to win the Women's Tag Team Championships for the second time, which also made Bayley a double champion. At the Backlash pay-per-view on June 14, Bayley and Banks successfully defended the tag team titles for the first time in a triple threat tag team match against Bliss and Cross, and The IIconics. Bayley successfully defended her title against Nikki Cross at The Horror Show at Extreme Rules on July 19, and against Asuka at SummerSlam on August 23. A week later at the Payback pay-per-view, Bayley and Banks defended the WWE Women's Tag Team Championships against the newly-formed team of Nia Jax and Shayna Baszler, where they lost the titles. On the September 4 episode of SmackDown, after Bayley and Banks lost to Jax and Baszler in a rematch, Bayley turned on Banks by attacking her in the ring, thus disbanding their team. At Clash of Champions, Bayley retained her title against Asuka, with Banks attacking her afterwards. On the October 9 episode of SmackDown, Bayley retained against Banks via disqualification, reaching the 365 day mark as champion, while also being announced to defend the title against Banks at Hell in a Cell, where she lost the title to Banks, thus ending her reign at 380 days. On the October 30 episode of SmackDown, Bayley challenged Banks to a title rematch the following week, which Banks accepted. On the subsequent episode of SmackDown, Bayley failed to regain the title. At Survivor Series, Bayley was the captain of Team SmackDown, but she was eliminated by Peyton Royce. At the 2021 Royal Rumble, Bayley entered at number one; however, she was eliminated by Bianca Belair. After failing to win the Royal Rumble, Bayley would defeat two members of the Riott Squad on the February 5 and 12 episodes of SmackDown. On night two of WrestleMania 37, Bayley came out and started insulting the hosts Hulk Hogan and Titus O'Neil, accusing the legends of disrespect, only to get beaten up by The Bella Twins. It was later revealed that Bayley would face Bianca Belair for the SmackDown Women’s Championship at WrestleMania Backlash. At the event, Bayley was unsuccessful. Bayley was also unsuccessful a second time on capturing the title in a Hell in a Cell match at the eponymous pay-per-view. On July 9, WWE announced that Bayley suffered an injury that would sideline her for nine months.
At SummerSlam on July 30, 2022, Bayley returned after a year out of action, forming an alliance with Iyo Sky (formerly known as Io Shirai) and Dakota Kai while confronting Belair after her Raw Women's Championship defense against Becky Lynch, resuming their feud and moving Bayley back to the Raw brand. On the August 8 episode of Raw, they challenged Belair, Alexa Bliss, and Asuka to a six-woman tag team match at Clash at the Castle, which they accepted and won. Due to her pinning Belair at Clash at the Castle, Bayley challenged Belair to a ladder match for the Raw Women's Championship at Extreme Rules, which was made official. At the event, Bayley was unsuccessful in winning the title. At Crown Jewel on November 5, Bayley again failed to win the title in a Last Woman Standing match. Three weeks later at Survivor Series WarGames on November 26, Damage Control competed in a WarGames match, teaming with Nikki Cross and Rhea Ripley against Belair, Bliss, Asuka, Mia Yim and Becky Lynch, but lost when Lynch pinned Kai after a diving legdrop from the top of the cage through a table. At the Royal Rumble on January 28, 2023, Bayley entered the women's Royal Rumble match at number six, and eliminating five women, including Lynch, before being eliminated by Liv Morgan. On night one of WrestleMania 39, Damage Control lost to the team of Becky Lynch, Lita, and Trish Stratus.
As part of the 2023 WWE Draft, Bayley, along with stablemates Kai and Sky, was drafted to the SmackDown brand. On the May 12 episode of SmackDown, Kai and Bayley failed to win the WWE Women's Tag Team Championships from Liv Morgan and Raquel Rodriguez. After Morgan and Rodriguez vacated the titles due to Morgan suffering an injury, Bayley and Sky pariticpated in a fatal four-way match for the vacant titles on the May 29 episode of Raw, but the match was won by Ronda Rousey and Shayna Baszler. On the June 9 episode of SmackDown, Bayley defeated Mia Yim to qualify for the women's Money in the Bank ladder match. At Money in the Bank, Bayley pushed Sky, who also participated in the match, off the ladder when Sky was trying to grab the briefcase. Bayley was later handcuffed to Becky Lynch by Sky to grab the briefcase and win the match. Nevertheless, Bayley helped Sky cash in the Money in the Bank breifcase to win the WWE Women's Championship at SummerSlam. Over the next few months, Bayley helped Sky retain her title on several occasions while Asuka and Kairi Sane joined Damage Control. At Survivor Series WarGames on November 25, Bayley, Sky, Asuka and Sane were defeated by Belair, Lynch, Charlotte Flair and Shotzi after Lynch pinned Bayley.
At the Royal Rumble on January 27, 2024, Bayley won the women's Royal Rumble match from the number three spot by last eliminating Liv Morgan. She also set a new record for the longest time spent in a single women's Royal Rumble match at 1:03:03, beating Rhea Ripley's record from the previous year. On the February 2 episode of SmackDown, Bayley left Damage Control after she confronted Sky, Sane, and Asuka before suffering a group attack, turning face in the process. She then announced she would challenge Sky at WrestleMania XL for the WWE Women's Championship, turning face for the first time since 2019. On night two of WrestleMania XL on April 7, Bayley defeated Sky to win her second WWE Women's Championship. On the April 19 episode of SmackDown, Bayley defended her title for the first time against Naomi, but the match ended in a no contest after Tiffany Stratton attacked both Naomi and Bayley. At Backlash France on May 4, Bayley successfully defeated Naomi and Stratton in a triple threat match to retain her title. At Clash at the Castle: Scotland on June 15, Bayley successfully retained her title against Piper Niven in the latter's home country. At SummerSlam on August 3, Bayley lost the title to Queen of the Ring winner Nia Jax, ending her reign at 118 days. At Bad Blood on October 5, Bayley failed to regain the title from Jax after interference from Stratton.