Maffia began her official acting career in off-Broadway and off-off-Broadway productions. In 1994, she played Carmen in director Ron Howard's film The Paper. Soon after, she landed a role on the television series Chicago Hope. Maffia's television career continued as she played Grace Alvarez, the forensic pathologist for the Violent Crimes Task Force for four seasons on Profiler. She has had guest-starring and recurring roles on shows such as ER, The West Wing, and Law & Order.