Notable for his Irish Film & Television Award-winning performance in the 2000 movie Saltwater, he is also well known for his writing and directing work on the acclaimed films Pentecost (2011) and The Stag (2013). His television credits include roles in Moone Boy, Your Bad Self, and Sea of Souls.
While studying English at University College Dublin, he was active in Dublin's Fly by Night Theatre Company.
A prolific London stage actor, he appeared in The Weir, The Caretaker, Glengarry Glen Ross, The Lieutenant of Inishmore, and numerous other plays.
The son of cookbook author Brenda Costigan, he grew up in Dublin, Ireland.
He co-starred with Brendan Gleeson in the 1997 feature film I Went Down.