AJ Lee took part in the third season of NXT beginning in September 2010. The show mixed professional wrestling and reality competition formats as six female participants competed to be WWE's "next breakout star". Primo was assigned as her "WWE Pro", the role of her mentor in the storyline. She performed as a face on the show and WWE adapted her "nerd" fandom to her character. Throughout the season, a relationship between AJ and Primo was teased, with them ultimately kissing on the finale. She also developed an on-screen friendship with fellow competitor, Kaitlyn. On November 23, AJ was eliminated in third place.
AJ made her main roster debut on the May 27, 2011, episode of SmackDown as part of a tag team with Kaitlyn, referring to themselves as "The Chickbusters". Along with their mentor Natalya, they feuded with the trio of Alicia Fox, Tamina Snuka, and Rosa Mendes for two months. In late July, AJ began a brief storyline on NXT Redemption as the girlfriend of Hornswoggle and feuded with Maxine. Meanwhile on SmackDown, she was attacked by Natalya, who turned on her protégé and allied with Beth Phoenix to form the Divas of Doom. AJ and Kaitlyn repeatedly lost to the Divas of Doom over the following months, upsetting Kaitlyn.
By November 2011, AJ was placed in an on-screen romance with Daniel Bryan, who won the World Heavyweight Championship the next month and developed heel traits. Despite AJ's declaration of love for Bryan, Bryan avoided saying he loved her in return. On January 13, 2012, while accompanying Bryan for his title defense, she was accidentally struck by Big Show and carried off on a stretcher as part of the storyline. She returned on February 3, preventing Bryan from being attacked by Big Show. In March, Bryan started acting verbally abusive towards AJ but she stood by him. At WrestleMania XXVIII on April 1, after sharing a "good luck kiss" with Bryan, he was surprised by Sheamus and defeated in 18 seconds. Bryan blamed AJ for his loss of the World Heavyweight Championship and ended their relationship. AJ made multiple attempts to mend their relationship but Bryan spurned her and left her distraught. As a result, she attacked Natalya and Kaitlyn when they attempted to comfort her, marking her character's transition to "mentally unstable".
AJ turned her affections to Bryan's rival and WWE Champion CM Punk as well as Kane. At No Way Out on June 17, AJ interfered in a triple threat match for the WWE Championship between Punk, Bryan, and Kane, helping Punk retain his title by distracting Kane. As Bryan and Punk's feud progressed, AJ was announced as the special guest referee for their title match at Money in the Bank. Bryan made advances on AJ in an attempt to influence her, however, she focused her attention on Punk. Enraged by his disinterest on the July 2 episode of Raw, she interfered in his match and shoved him, along with Bryan, through a ringside table. After they made amends, she proposed to him but Bryan countered with a proposal of his own; Punk rejected her offer and she slapped both men. At Money in the Bank on July 15, as referee, AJ counted Punk's pinfall on Bryan, resulting in a successful title defense for Punk; as Punk celebrated over a fallen Bryan, AJ was left alone. The next night, Bryan proposed to her again and she accepted.
During the exchange of vows at Raw 1000, AJ announced that WWE chairman Vince McMahon had offered her the job of Raw General Manager and left Bryan at the altar. Her on-screen authority role began on July 30, where she alleged that Bryan only wanted the legal leverage to have her committed and forced him to undergo his own psychological evaluation. AJ continued to exact revenge on both Bryan and Punk throughout her tenure, denying their requests and booking them in matches against their wishes. On August 27 and September 24, she was involved in separate altercations with Vickie Guerrero and Paul Heyman, in which she attacked them. AJ was reprimanded by the board of directors, and the two demanded the General Manager position for themselves, deeming her too childish.
AJ stepped down from her General Manager duties on October 22, becoming embroiled in a scandal storyline with John Cena. Vickie Guerrero alleged that they had an affair and presented various material over the next month to support her claim. AJ and Cena denied the accusations and eventually formed a relationship, though Cena quickly grew reluctant due to her erratic behavior. Meanwhile, Cena feuded with Guerrero's client, Dolph Ziggler, over Ziggler's Money in the Bank contract. During their match at TLC on December 16, AJ turned heel by interfering and pushing Cena off a ladder, causing him to lose. She solidified a relationship with Ziggler the next night on Raw and they teamed together against Cena and Guerrero in the main event, which ended in disqualification after the debuting Big E Langston attacked Cena on her behalf. Subsequently accompanied by Langston as her bodyguard, she explained that Cena had "toyed with" her emotions and "broke her heart", so she helped Ziggler "break" him.
In March 2013, AJ's storyline rivalry with ex-boyfriend Daniel Bryan was reignited when they traded insults backstage. She and Langston assisted Ziggler in victories over Bryan and his tag team partner Kane, which led to Ziggler and Langston losing to them in a WWE Tag Team Championship match at WrestleMania 29 on April 7, despite her interference. The next night on Raw, she and Langston accompanied Ziggler as he cashed in his Money in the Bank contract on Alberto Del Rio to win the World Heavyweight Championship.
AJ won a battle royal on April 22, 2013, to become the number one contender to Kaitlyn's WWE Divas Championship. Kaitlyn soon began a storyline where she received gifts from a secret admirer. On June 10, after setting up Langston to pose as the admirer, AJ revealed it to be a mind game, berated Kaitlyn and left her in tears. Six days later at Payback, AJ defeated Kaitlyn to capture her first Divas Championship. While she continued to mock Kaitlyn, they participated in the first ever in-ring contract signing for a Divas Championship bout. At Money in the Bank on July 14, AJ won their rematch but later in the show caused Ziggler to lose his own rematch for the World Heavyweight Championship. She hit his opponent, Alberto Del Rio, with her title belt to protect him from further head injury, prompting a disqualification. Angered by her unwanted action, Ziggler ended their relationship. She exacted revenge by costing him another match, then attacked him with Langston. On August 2, Langston was banned from attending her matches. However, AJ again retained the title from Kaitlyn, who was betrayed by Layla. Kaitlyn and Ziggler ultimately joined together to defeat AJ and Langston in a mixed tag team match at SummerSlam on August 18.
On August 26, AJ interrupted the cast of Total Divas during a post-match segment and insulted them. She later vowed to defeat every member of the cast, and enlisted Tamina Snuka as her bodyguard. Throughout the remainder of the year, AJ successfully defended the championship against the trio of Brie Bella, Naomi, and Natalya at Night of Champions, Brie Bella at both Battleground and Hell in a Cell, and Natalya at TLC. She also captained a team at Survivor Series in a traditional seven-on-seven elimination tag team match against the entire cast, which her team lost.
In January 2014, AJ became the longest-reigning Divas Champion at the time. After fending off title contenders Cameron and Natalya, AJ renewed her on-screen rivalry with SmackDown General Manager Vickie Guerrero, who forced her to defend the Divas Championship in a 14-woman match at WrestleMania XXX. AJ won the match on April 6, marking the first time the championship had been contested for at WWE's flagship event. The next night on Raw, AJ challenged the debuting Paige to an impromptu title match and was defeated, ending her then-record reign at 295 days. Lee was subsequently granted time off.
Upon her return on June 30, AJ switched to a face role and was no longer accompanied by Tamina. She challenged Paige to an impromptu rematch and won back the Divas Championship. They started pretending to be best friends in a facetious manner. When AJ retained the title from Paige at Battleground, their act escalated into unprovoked attacks. At SummerSlam on August 17, AJ lost the championship to Paige. Their storyline was then intertwined with that of Nikki and Brie Bella, at the behest of Stephanie McMahon, who granted Nikki a championship opportunity. A triple threat match ensued at Night of Champions on September 21, where AJ became a record-tying three-time Divas Champion. Her feud against Paige concluded with a victory at Hell in a Cell in October. She changed focus to Nikki Bella, whose sister, Brie, was involved as her "personal assistant". AJ quickly lost the championship to Nikki at Survivor Series on November 23, due to a distraction by Brie. After losing the rematch at TLC the following month, Lee took time off to heal a pre-existing neck injury.
AJ returned on the March 2, 2015 episode of Raw, saving her former rival Paige from an attack by Nikki and Brie Bella. AJ and Paige allied together to defeat the Bella Twins at WrestleMania 31 on March 29. A six-woman tag team match the next night on Raw wound up being her final match, as WWE announced her retirement from in-ring competition on April 3.