Mulhern attended Pascack Hills High School in Montvale, New Jersey.
Matt Mulhern was trained as an actor by William Esper at Mason Gross School of the Arts, where he received a BFA in Acting. He was first cast as Joseph Wykowski in Neil Simon's Tony Award winning Biloxi Blues. From there, he went on to a film, TV, and theater career as an actor, appearing in films such as One Crazy Summer, Extreme Prejudice, Biloxi Blues, and others.
New York theater includes: The One-Armed Man at Ensemble Studio Theater, Surviving Grace at the Union Square Theater, The Night Hank Williams Died at the Orpheum Theater, Wasted at the WPA, Regional appearances at La Jolla Playhouse in The Glass Menagerie, The Habitation of Dragons, at Pittsburgh Public Theater, and the National Tour of Death of a Salesman as Biff opposite Hal Holbrook.
On TV, Mulhern played the Lieutenant on the top ten CBS hit Major Dad. Past guest appearances include a recurring role on FX's Rescue Me, and an appearance on Fox's Fringe.
He has written and directed two films, Walking to the Waterline, which he also acted in, and Duane Hopwood, starring David Schwimmer.
He also has a novel, Crossing Open Spaces, published by CreateSpace in March 2009. Matt lives north of New York City with his wife, Karen, and sons, Connor and Jack.