Brian Asawa began his studies as a piano major at the University of California, Santa Cruz, ultimately switching his studies to singing under tenor Harlan Hokin. After two semesters there he transferred to UCLA where he studied under Virginia Fox and Kari Windingstad. In 1989 he began a masters degree in early-music interpretation at the University of Southern California in Los Angeles where he was a pupil of the British lutenist James Tyler. However, Asawa never finished this program as his performance career began to take off.
The singer's career was launched in 1991 when he became the first countertenor to win both the Metropolitan Opera National Council Auditions and an Adler Fellowship to the San Francisco Opera's Merola Opera Program. He made his professional opera debut at the San Francisco Opera in 1991 in Hans Werner Henze's Das verratene Meer where he also sang the Shepherd in Tosca and Oberon in Benjamin Britten's A Midsummer Night's Dream in 1992. While at the SFO he continued further voice studies with Jane Randolph. He also made his first opera appearance in New York City in 1992 at the Mozart Bicentennial celebration at Lincoln Center, singing the title role in Mozart's Ascanio in Alba with the Mostly Mozart Festival Chorus and the New York Chamber Symphony under conductor Ádám Fischer.
In 1993, Asawa was awarded a career grant from the Richard Tucker Music Foundation and that same year made his debut at the Santa Fe Opera as Arsamene in George Frideric Handel's Xerxes. In 1994 he became the first countertenor to win the Plácido Domingo Operalia International Opera Competition, and made debuts at the Metropolitan Opera as the Voice of Apollo in Benjamin Britten's Death in Venice and Glimmerglass Opera as Ottone in Claudio Monteverdi's L'incoronazione di Poppea. He was chosen Seattle Opera's Artist of the Year for the 1996–97 season.
Asawa's other career highlights include Orlofsky in Die Fledermaus at San Francisco Opera and San Diego Opera; Tolomeo in Giulio Cesare at Metropolitan Opera, Bordeaux, Opera Australia, Royal Opera House, Covent Garden, Paris Opera, Gran Teatre del Liceu in Barcelona, and Hamburg State Opera; Arsamene in Serse at Los Angeles, Cologne, Seattle, and Geneva; Admeto in Admeto at Sydney, Montpellier and Halle; Baba The Turk in The Rake's Progress at San Francisco and for Swedish television; Fyodor in Boris Godunov at the Gran Teatre del Liceu, Endimione in La Calisto in Brussels, Oberon in A Midsummer Night's Dream at San Francisco, Houston, London Symphony Orchestra and Lyon; Ascanio in Ascanio in Alba at the Lincoln Center; Farnace in Mitridate, re di Ponto at Opera National de Lyon and Paris Opera; Nero in L'incoronazione di Poppea in Sydney; Orfeo in Orfeo ed Euridice, La Speranza in L'Orfeo and L'Umana Fragilita/Anfinomo in Il ritorno d'Ulisse in Patria at Netherlands Opera; David in Saul and Belize in Angels at the Bavarian State Opera, and Sesto in Giulio Cesare at COC in Toronto.
Asawa is the nephew of sculptor Ruth Asawa.
Brian Asawa's discography includes four solo recital discs ranging from Dowland and Edmund Campion to Rachmaninoff and Ned Rorem. Opera recordings include Farnace in Mitridate for Decca, Arsamene in Serse for Conifer and Oberon in A Midsummer Night's Dream for Philips with the London Symphony Orchestra under Sir Colin Davis.