He and Kate Winslet, whom he met on the set of Hideous Kinky, married on 22 November 1998 in Reading, Berkshire, Winslet's hometown. They had a daughter, Mia Honey Threapleton, born on October 12, 2000 in London. However, the two separated in September 2001 and divorced on 13 December 2001.
In 2008, Threapleton married his second wife, Julie Vuorinen, a school administrator and teacher to special needs students. As of 2008, the two were expecting a child, Jim's second.