The elder of two boys, he has a younger brother Robin. 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 Winslet (born 12 October 2000 in London). However, the two separated in September 2001 and divorced on 13 December 2001.

His first work as a Director (and writer) was the film Extraordinary Rendition, starring Omar Berdouni and Andy Serkis, which premiered at the 2007 Locarno Film Festival.

In 2008 Threapleton married his second wife, Julie Vuorinen, a school administrator and Teacher to special needs students. They have a daughter, Olivia, born in 2009. They had a second daughter, Georgia, in 2013.