From Cork City, Cillian made his TV debut on TG4 as Danny Flynn in The Running Mate. Before 6Degrees, he had various roles in theatre, short films and television such as Salome, Someone Who'll Watch over Me, Boat Memory (Laurence Olivier Theatre London), Uncle Billls Barrel, An Cosc, Singlehanded and BBC NI/TG4's Seacht.
Most recently playing Christian Ramsay in Ridley Scott's Halo: Nightfall Cillian is currently in rehearsals for Leesa Harker's comedy play Slimmer for Christmas.