At the age of seven, she made her professional debut by starring in the play The King and I by the Repertory Philippines. She has since appeared in other plays: Cat On A Hot Tin Roof, Fiddler On The Roof, The Rose Tattoo, Annie, The Sound Of Music, The Goodbye Girl, Paper Moon, The Fantasticks and Flower Drum Song.
She began her professional music career at the age of ten when she recorded her first album, Small Voice, which received a gold record. She has also hosted her own musical television show, Love, Lea, and opened for Stevie Wonder during his concerts in Manila. At age 13, she won three Aliw Awards for Best Child Entertainer from 1981 to 1893.
Her biggest breakthrough came when she was selected to play the leading role of Kim in the new musical Miss Saigon in 1989. The play, set during the final days of the Vietnam War, tells the story of Kim, a poor Vietnamese girl, and Chris, an American soldier who fall in love. For this performance, Lea Salonga was given the Laurence Olivier Award for Best Actress in a Musical or Entertainment for the year 1989/1990. From its original London home, Miss Saigon moved to Broadway. Lea Salonga subsequently garnered Tony, Drama Desk and Outer Critics Circle Awards.
In 1993, Lea Salonga played the role of street waif Eponine in the Broadway production of Les MisÚrables, then flew to Los Angeles to perform the song "A Whole New World" (of Disney's Aladdin) at the 65th Annual Academy Awards, where the song won an Oscar. In the same year she released her self-titled international debut album with Atlantic Records, which has gone platinum and gold in parts of Southeast Asia.
Lea also was the singing voice of Jasmine for Aladdin (1992) and Fa Mulan for Mulan (1997), films by Disney.