McHattie was born in Antigonish, Nova Scotia on February 3, although his year of birth has been given as 1945, 1946, 1947, and 1948, depending on the varying sources.
In Canada, he appeared in Canada: A People's History as Canadian hero Major-General Sir Isaac Brock, and in The Rocket (Maurice Richard) as coach Dick Irvin. He portrayed Jacques Pasquinel in Centennial. He portrayed an extraordinary USMC sniper (based on real life sniper Carlos Hathcock) in the JAG season one episode "High Ground". In 1976 McHattie played James Dean in the television movie James Dean, a television adaptation of the biography written by James Dean's friend and Writer Bill Bast.
An alumnus of the American Academy of Dramatic Arts, he has appeared in many films and television shows including Star Trek: Deep Space Nine, Star Trek: Enterprise, Highlander: The Series, and American Playhouse's Life Under Water (1989). His roles include 300, A History of Violence, The Fountain, Secretary, Shoot 'Em Up, Life with Billy, One Dead Indian, Beverly Hills Cop III.
McHattie appeared in several episodes of Seinfeld (beginning with "The Pitch") where he played Dr. Reston, Elaine Benes' manipulative Psychiatrist boyfriend. He appeared in two episodes of The X-Files. From 1998 - 2000 McHattie had a recurring role in the Canadian-made TV series Emily of New Moon, based upon the 1923 novel by Lucy Maud Montgomery. From 1999 - 2001, he portrayed Sgt. Frank Coscarella in the Canadian police procedural drama, Cold Squad.
Since 2005, he has appeared as Captain/Commander Healy in the first eight of the Jesse Stone series TV movies, which are based on the novels of Robert B. Parker. He did not appear in the latest instalment however.
In 2009, McHattie appeared in the Canadian IFC film Pontypool and in the Canadian thriller Summer's Blood as Gant Hoxey, alongside Twilight Actress Ashley Greene, who portrays Summer. He co-starred with Felicia Day and Kavan Smith in the Gothic adaptation of Red Riding Hood, Red: Werewolf Hunter. In 2015, he appeared in the supernatural thriller Pay the Ghost.
