Harrington's first film appearance was Sanctimony as Hank. He was later cast in Showtime's Out of Order and had a recurring role as Criminal Ronald Basderic on CSI: Crime Scene Investigation during the 2012–13 season. He played the fallen angel Bartholomew, in the ninth season of Supernatural. He has a starring role The CW's drama series The Secret Circle. He also worked at Sealand Oceanariums in Nanaimo, British Columbia.
