[3] Larsen was tapped by a talent scout to play a small uncredited role in 1951 movie Operation Pacific.

Larsen's career was most notable for his work in four weekly television series, including playing Bart Adams in The Hunter (1954),[5]: 487  Brave Eagle (1955), Northwest Passage (1958) (in which he starred as Major Robert Rogers),[5]: 772  and The Aquanauts (1960).

[3] In the 1958–1959 season, Larsen starred in the M-G-M/NBC series Northwest Passage, the story of Major Robert Rogers, an American soldier in upstate New York during the French and Indian War.

[7] In 1959, Larsen guest starred on the CBS series Men into Space in the role of Jim Nichols in the episode " Christmas on the Moon".

In 1960–1961, Larsen appeared as 36-year-old former Navy diver Drake Andrews in the CBS adventure series The Aquanauts, an Ivan Tors Production renamed in March 1961 as Malibu Run.

[8] After The Aquanauts, Larsen appeared as Jack Bennett in the 1961 episode "Blondes Prefer Gentlemen" of the ABC series The Roaring Twenties, with Donald May, Rex Reason, and Dorothy Provine.

[3] Larsen's later acting work was in Women of the Prehistoric Planet (1966), three films made in the Philippines, Caxambu!, (1967) Mission Batangas, where he began a new phase as a director as well as an actor and The Omegans (1968) with Ingrid Pitt.

He travelled to Japan to direct and co-star in The Walking Major, Mission Batanagas as Colonel Turner (1968), then did Night of the Witches as Reverend Ezra Jackson (1970), The Trap on Cougar Mountain (1972), Whitewater Sam in the title role (1977), and his last appearance, Young and Free (1979).