Hamsher is a Massachusetts native who lived in Fitchburg and then Attleboro. Her family moved to Seattle when she was eight years old. She attended Roosevelt High School. She went on to attend Mills College in Oakland, California, and studied abroad in London. In college Hamsher worked as a reporter covering punk rock and politics for the "San Francisco Bay Guardian". She also edited "Damage", a punk rock fanzine. After college she moved to Los Angeles, where she was accepted into the Peter Stark Producing Program at the USC School of Cinema-Television. She received her M.F.A. in 1988.