Mwine began appearing in stage productions in 1992, appearing as the con man posing as Sidney Poitier's son in Six Degrees of Separation, and in The Riddles Of Race, Circa '68 in 1994, In 1992 and 1997, Mwine was nominated for a Helen Hayes Award for Outstanding Lead Actor in a Non-Resident Production, for his role in Six Degrees of Separation at the National Theatre and Nomathemba at the Kennedy Center in Washington, D.C. He played Julius Van George in Scent of the Roses at the Seattle Contemporary Theatre in 1998.