He originally attended the College of the Holy Cross after high school but transferred and studied at the American Academy of Dramatic Arts in New York City.

At this time, he changed his name to Mark Goddard at the suggestion of his friend and mentor Chuck Connors of The Rifleman.

[citation needed] Goddard appeared as Norman Tabor in the 1960 episode "Surprise Party" of the CBS anthology series The DuPont Show with June Allyson.

He was cast as Sheldon Hollingsworth in the 1960 episode "To See the Elephant" of the ABC Western series The Rebel, starring Nick Adams.

That same year he guest starred as a wild killer named “Boyd” in the episode “Journey For Three” on the TV Western series Gunsmoke (S9E36).

[4] Goddard guest-starred on three ABC series, The Fugitive, The Mod Squad, and The Fall Guy and for a while, moonlighted as a Hollywood agent.

He made a cameo appearance in the 1998 reboot film Lost in Space as the general in charge of the Jupiter Mission and superior officer to his former character Major Don West.

[8] Goddard's first marriage was to Marcia Rogers in 1960, which lasted until their divorce in 1968; the couple had two children, Melissa and Michael.

Goddard and Rogers were amongst the last people to see Karyn Kupcinet, hosting a dinner on the night of November 27, 1963.