Lambert grew up in Rancho Peñasquitos, San Diego, California and attended Deer Canyon Elementary School, Mesa Verde Middle School, and Mt. Carmel High School, where he was in theater, choir, and a jazz band.
Lambert has been a stage actor since he was about 10 years old; he was cast as Linus in San Diego's Lyceum Theater's production of You're a Good Man, Charlie Brown. He also played a part in The Ten Commandments at the Kodak Theatre alongside Val Kilmer. He was the understudy for the part of Fiyero in the touring and Los Angeles casts of the musical Wicked. Since 2004 he regularly performs at the Zodiac Show, which was co-created by Carmit Bachar of the Pussycat Dolls. He also performs at the Upright Cabaret.
Lambert auditioned for the eighth season of American Idol in San Francisco, California. During his initial audition he sang Queen's "Bohemian Rhapsody". Both Kara DioGuardi and Simon Cowell criticized him for being theatrical, however he moved on to the Hollywood rounds. In Hollywood, Lambert sang Cher's "Believe", a risky song choice which paid off for him in the end as he made the Top 36.
For his semi-final performance he sang The Rolling Stones' "(I Can't Get No) Satisfaction". All the judges praised him; however, Simon remarked that parts of it were "excruciatingly bad" while other parts were "brilliant". He called it a "love it or hate it performance". Following that performance, Lambert was voted into the Top 13.
On Michael Jackson week (Top 13), he sang "Black or White" leading to praise from all four judges. After his Top 13 performance of Black or White by Michael Jackson, judge Paula Abdul predicted that he would go on to be the winner or runner-up of the competition. The following week, Lambert sang a modified version of Johnny Cash's "Ring of Fire". While Randy, Paula, and Kara all liked his performance, Simon called it "indulgent rubbish". On Motown week (Top 10), Lambert distanced himself from the prior week's performance, singing a slowed down, acoustic version of The Miracles' "The Tracks of My Tears". The judges all liked it, with Simon proclaiming that he had really emerged as a star that night. Smokey Robinson, Motown week's mentor, gave Adam a standing ovation. The next week he sang Wild Cherry's "Play That Funky Music". Simon praised him on his brave performance, while Paula described him as a "true genius" whose performance "shattered expectations".
For his Top 8 performance (Year You Were Born) Adam sang the 2001 Gary Jules' arrangement of "Mad World", a song written and performed by British band Tears for Fears in 1982. Because the show had exceeded its time slot, only judge Simon Cowell gave a critique, which he did by simply giving Lambert a standing ovation. The next night, the other judges agreed that a standing ovation was the best critique of Adam's performance.
Adam Lambert, Danny Gokey and Kris Allen are the only final contestants not to have been in the Bottom 3.
Photos of Lambert kissing another man were shown and discussed by conservative commentators on The O'Reilly Factor, they agreed that the images would likely have no impact on the competition because the focus remains on the singers' talent. Lambert confirmed that the photos were of him, stating he had nothing to hide and has always been open about his life.