Delaney soon added screen acting to his resume, starring in the 2003 short film An Cuainín, and in 2005 appearing in the Irish television series Pure Mule and The Clinic.
[2] It was in 2006 that he first appeared before international audiences as Irish revolutionary Teddy O'Donovan in Ken Loach's The Wind That Shakes the Barley, opposite Cillian Murphy.
[4] Delaney was a cast member of the Showtime series The Tudors in which he plays Anne Boleyn's brother George[3] alongside Jonathan Rhys Meyers as King Henry VIII.
[5] In late 2007, Delaney appeared on stage at the Tricycle Theatre in the role of Father Flynn in John Patrick Shanley's play Doubt: A Parable.
Between 2013 and 2014, he starred in Martin McDonagh's dark comedy play The Cripple of Inishmaan alongside Daniel Radcliffe, which started out in London's West End and then transferred to Broadway.