García was hired by the World Wrestling Federation as a ring announcer in 1999. She made her debut on the August 23, 1999 episode of Raw is War in Ames, Iowa. She was involved in her first angle on the September 13 episode of Raw is War, when Jeff Jarrett applied a figure four leglock to her after she angered him by announcing his loss by disqualification to Luna Vachon.
Garcia's second angle occurred on the December 13, 1999 episode of Raw. Lilian introduced Miss Kitty for a Women's Championship chocolate pudding pool match. After Lilian announced her, Miss Kitty grabbed the mic and informed Lilian that she was now to be known as "The Kat". Her opponent, Tori, came out for their match and right after the two women began, X-Pac came poolside in a skin diving suit complete with snorkel, flippers, and goggles. As he was adjusting his goggles, Tori jumped on his back causing both of them to fall into the pool with X-Pac landing up on top of Tori, giving Miss Kitty an easy pinfall. Lilian announced the winner as "Miss Kitty", which infuriated The Kat, who threw Lilian into the pool of pudding.
Garcia sang the national anthem of the United States of America for the first time on February 11, 2000, at a house show in Denver, Colorado. She sang the anthem once again, before Raw went on the air on February 14, 2000, in San Jose, California. Her first televised performance aired on April 2, 2000, where she opened WrestleMania 2000 in Anaheim, California. Following the September 11 attacks, Garcia sang "The Star-Spangled Banner" on the September 13, 2001, episode of SmackDown!, receiving a standing ovation.
In August 2002, García briefly feuded with rival announcer Howard Finkel after Finkel left her to be decimated by 3-Minute Warning, culminating in an "evening gown versus tuxedo match" that Garcia won with the assistance of Stacy Keibler and Trish Stratus. During the Memorial Day episode of Raw on May 26, 2003, Garcia was singing "America the Beautiful" to the crowd when she was interrupted by La Résistance members Sylvain Grenier and René Duprée as they insulted America saying they should've been more like the French and they mocked the American people by calling them "fat and ugly". Just then, Garcia's friend, Co-General Manager Stone Cold Steve Austin, came down to the ring and tossed Grenier out of the ring and delivered a Stunner to Duprée. After the two Frenchmen walked out of the ring, Austin sang America the Beautiful with Lilian and the two celebrated with a beer bash. During the November 24 episode of Raw, Garcia announced Trish Stratus as the winner of a bra and panties match over Jackie Gayda. Infuriated, Gayda stripped Garcia down to her black bra.
In June 2005, García began an on-screen romance with wrestler Viscera. The angle saw García propose to Viscera, stating that she wanted to marry him during the Vengeance pay-per-view on June 26. The angle ended at Vengeance when Viscera rejected Garcia in favor of The Godfather's Hos. The angle was briefly resurrected eleven months later when Viscera proposed to Garcia on the May 22, 2006, episode of Raw, but was interrupted by Umaga before receiving an answer. On the June 5, 2006 episode of Raw, Garcia suffered a sprained wrist when wrestler Charlie Haas inadvertently knocked her to the ground as she stood on the ring apron. One week later, the accident was metamorphosed into a storyline, with Haas incurring the wrath of Viscera. The storyline ended on the July 10, 2006 episode of Raw, when Viscera accidentally performed a Samoan drop on Garcia while confronting Haas. Garcia was removed from television for several weeks in order to sell the Samoan drop.
On the April 2, 2007, episode of Raw, García was humiliated in the ring when her blue satin frilled skirt was torn off by Bobby Lashley, revealing her black panties after Vince McMahon attempted to hide his newly shaven bald head under her skirt. She returned to announcing on the July 2, 2007 episode of Raw after taking time off to recover from an injury. On the August 6, 2007 episode of Raw, Garcia announced her new album. Lilian then started a feud with Jillian Hall, who claimed to be a better singer than Lilian. The next week, she competed in WWE Idol, in which she sang "New York, New York" before being interrupted by Santino Marella.
In addition to announcing on Raw and pay-per-view matches, Garcia also announced on WWE Superstars, making her first appearance on April 23, 2009. On the September 21, 2009, episode of Raw from Little Rock, Arkansas, Jerry Lawler announced to the live audience that it was Garcia's final night with WWE. Garcia then made an emotional speech in the ring, thanking the fans and all of her colleagues. The final match she announced live featured Randy Orton, Chris Jericho, and Big Show taking on the team of John Cena, Montel Vontavious Porter, and Mark Henry, although a match between Primo and Chris Masters was taped earlier that evening and aired three days later on WWE Superstars, marking her final television appearance.
Garcia made a special appearance before the Madison Square Garden audience on November 16, 2009, singing "The Star-Spangled Banner" prior to the evening's Raw telecast. Garcia filled in for Raw ring announcer Justin Roberts on April 19, 2010, due to being stranded in Europe with other WWE Superstars.
On December 5, 2011, WWE announced that Garcia would be returning to ring announcing full-time, appearing on SmackDown. She returned at the December 6 tapings of the show. She also served as the ring announcer for Main Event and pay-per-views. Garcia suffered accidents prior to SmackDown tapings in 2012. While heading to the ring prior to the March 13 taping in Columbus, Ohio, the strap on her left shoe broke. One month later, during the April 17 taping in London, England, she tripped over pyrotechnic equipment on the top of the stage and fell down on the ramp, landing on her knees. On the April 19, 2013, episode of SmackDown, Garcia was instructed dance steps by Fandango and insulted.
On the June 6, 2014, episode of SmackDown, she was involved in a confrontation with Alicia Fox after Fox lost a match to Natalya. On October 20, 2014, after Justin Roberts was released from WWE, Garcia returned as the full-time ring announcer for Raw. Lilian returned from knee surgery on May 31 at Elimination Chamber. On August 1, 2016, Garcia announced her departure from WWE.
Garcia made a one-night return on December 14, 2016, at WWE Tribute to the Troops, where she sang the American national anthem. She made another special appearance before the audience in Phoenix, Arizona on July 4, 2017, singing "The Star-Spangled Banner" prior to the evening's SmackDown Live telecast. She was also the ring announcer for the finals of the Mae Young Classic on September 12, 2017. On January 22, 2018, on the Raw 25 Years special episode, Garcia was honored as part of a segment involving women considered legends that contributed to the company's success, including the Bella Twins, Maryse, Kelly Kelly, Torrie Wilson, Michelle McCool, Terri Runnels, Maria Kanellis and the Hall of Famers Jacqueline and Trish Stratus. She announced the first ever WrestleMania Women's Battle Royal on WrestleMania 34's pre-show on April 8, 2018. On October 28, 2018, she announced the first ever WWE all-women's pay-per-view WWE Evolution. On the July 22, 2019 episode of Raw, Garcia made a special appearance.
On May 13, 2024, Garcia made a one-night return on Raw, where she was asked by ring announcer Samantha Irvin to help introduce a King of the Ring quarterfinal tournament match between Gunther and Kofi Kingston. On the October 21 episode of Raw, Garcia would serve as announcer for the entire night in place of Irvin, who had announced her departure from WWE earlier that day. It was later announced that Garcia had re-signed with the company on a full time basis. On January 3, 2025, Garcia became the SmackDown ring announcer once again, switching roles with Alicia Taylor.