Martini spent a portion of his childhood moving around with his parents. When they settled in New York, he took the chance to study acting. He began his career in the Neighborhood Playhouse where a majority of his training with Michael Howard was spent in Manhattan. He later went on a hiatus from acting to attend the School of Visual Arts where he received a BFA in painting and sculpture.
Upon completing college, Martini worked steadily with small roles in television and film, his most notable roles being Cpl Fred Henderson in Steven Spielberg's Saving Private Ryan, Mack Gerhardt in CBS' The Unit and Agent Steve Goodrich in FOX's 24.