Barrowman was raised in Joliet, Illinois, and graduated from Joliet West High School in 1985. He is the son of a plant manager of the former Caterpillar Inc. tractor factory in Joliet. While still a high school freshman, he won parts in several musical productions. Between 1983 and 1985, he performed in productions of Hello, Dolly!, Oliver!, Camelot, L'il Abner and Anything Goes. He attended university in San Diego before returning to the United Kingdom in 1989. He holds a dual United Kingdom/United States passport, which enables him to work on both sides of the Atlantic.