Brian Mulligan debuted at the Metropolitan Opera while still a student at Juilliard, in December 2003 in Die Frau ohne Schatten. Since then, he has gone on to perform at some of the most important opera houses in the world, including San Francisco Opera (debut as Marcello in La Bohème), Opernhaus Zürich (debut as Yeletsky in Pique Dame), Lyric Opera of Chicago (debut as Enrico in Lucia di Lammermoor), Oper Frankfurt (debut as Prospero in Ades' The Tempest), Los Angeles Opera (debut as Prometheus in Die Vögel), New York City Opera (debut as Jake Wallace in La Fanciulla del West) and Houston Grand Opera (debut as Marcello in La Bohème).