Kim was introduced to World Wrestling Entertainment (WWE) employee Nora Greenwald (known on-screen as Molly Holly) by Jason Sensation in 2001; Greenwald encouraged Kim to send her videos and tapes to WWF officials, which eventually led to her contract. In October 2002, she was hired by WWE. She spent eight months training in Ohio Valley Wrestling (OVW) and appearing in house shows and dark matches before being called up to the main roster. After several weeks of vignettes showcasing Matrix-like effects aired on Raw, Kim debuted on the June 30, edition of Raw as a fan favorite, with a Matrix-inspired outfit.
Her first televised WWE match was a seven-woman battle royal in Buffalo, New York with the WWE Women's Championship, then held by an injured Jazz, on the line. Kim won the match by lastly eliminating Victoria. Kim held the title for four weeks, before losing it to Molly Holly on the July 28 edition of Raw. Subsequently, Kim formed an alliance with Holly to take on Trish Stratus. Stratus was later assisted by Lita, who had been absent from WWE television since injuring her neck in 2002. At Unforgiven on September 21, Stratus and Lita defeated Kim and Holly in a tag match. The four women continued to feud until November, when Kim was sidelined with a broken right collarbone. Kim returned to Raw in April 2004 and immediately reforged her alliance with Holly. At Bad Blood on June 13, she faced Lita, Stratus, and WWE Women's Champion Victoria in a Fatal Four-Way, which was won by Stratus.
Kim's last WWE match was a battle royal on October 19 at Taboo Tuesday, which was won by Trish Stratus. Kim was released from WWE on November 3, 2004. Kim was caught off guard by her release and was told that management wanted to take the women's division in a new direction. Following her release and the expiration of her ninety-day no-compete clause, Kim made sporadic appearances on the independent circuit, one being the All World Wrestling League (Michigan) and including wrestling matches in Japan.
After her contract expiration with TNA, Kim re-signed with World Wrestling Entertainment (WWE). Kim made her return on the March 27 episode of Friday Night SmackDown as a fan favorite, when she interrupted a WWE Divas Championship match between Michelle McCool and Maryse by attacking both Divas. Kim made her in-ring return on the March 30 episode of Raw in an 18-Diva tag team match on the winning team. Following this, Gail defeated Divas Champion Maryse in a non-title match, but failed to win the title when the two wrestled with the belt on the line.On June 29, Kim would be traded to Raw. She made her Raw in ring debut a week later teaming with Mickie James to defeat Divas Champion Maryse and Alicia Fox in a tag team match in which she pinned Maryse after an Inverted Stomp Facebreaker. In August she won a fatal four way match (which also included Kelly Kelly, Beth Phoenix, and Alicia Fox) to become the number one contender for the Divas Championship, but was unable to win the title when she lost to champion Mickie James one week later. On October 25, Kim represented Raw at Bragging Rights when she participated in a Six-Diva Interpromotional tag team match along side Melina and Kelly Kelly against SmackDown Divas Michelle McCool, Beth Phoenix, and Natalya in a losing effort.