Jason was born in Dublin. He graduated from Trinity College Dublin after studying at the Samuel Beckett Centre, Trinity College. His first job was the lead in a BBC Film called O Mary This London (1994), a part which required him to run for half a mile naked down Camden High Street for one of his opening scenes. After this movie he relocated to London and has appeared in many more films and TV series. He is married to actress Nicola Charles whom he met on the set of the Australian black comedy Muggers (2000). They have a daughter born in January 2005 named Freya. He has two younger brothers both working in the industry. Keith who is an Assistant Director, and Glen who has followed Jason into acting. Jason is also an accomplished Marathon runner and in 2005 won the Celebrity race representing The Leukemia Research Foundation at the London Marathon with a time of 2 hours 58 minutes. He is currently based in Los Angeles, California with his family.