Klattenhoff was nineteen when he moved from Nova Scotia to Toronto to persue a career in acting. He studied in multiple theatre workshops for several years and worked as a bartender. His first role was in the 2002 short film, Straight in the Face. In 2004 he starred alongside Rachel McAdams as Shane Oman in Mean Girls.
Outside of Homeland, Klattenhoff's additional credits in other shows and film include CTV's, Whistler, Men in Trees, Psych, Supernatural, 24 and recently, NBC's The Blacklist as FBI Agent Donald Ressler.