[1] Before he began appearing in films in 1947, Haggerty was a Brown University athlete and attended the Experimental Theatre of Vassar College.

[3][4][1] Usually cast as tough policemen or cowboys, Haggerty appeared in films such as Sands of Iwo Jima (1949), The Asphalt Jungle (1951), Angels in the Outfield (1951) and The Narrow Margin.

Haggerty appeared 21 times, including 19 in 1955 and 1956, as newspaperman Marsh Murdock in the ABC/Desilu western series The Life and Legend of Wyatt Earp.

In 1959, Haggerty portrayed Harry Moxton in the episode "No Laughing Matter" of the NBC crime drama Richard Diamond, Private Detective.

Haggerty appeared as a guest star in My Favorite Martian as Detective Sergeant Seeley in 1964's episode "Uncle Martin's Broadcast" and as a bank guard in 1965's "Hate Me a Little".