Robert Conrad was a graduate of Northwestern University, spending his first few years out of school supporting himself and his family by driving a milk truck and singing in a Chicago cabaret. Conrad befriended up-and-coming actor Nick Adams during this period, and it was Adams who helped Conrad get his first Hollywood work in 1957. A few movie bit parts later, Conrad was signed for a comparative pittance by Warner Bros. studios, and in 1959 was cast as detective Tom Lopaka on the weekly adventure series Hawaiian Eye. Upon the 1963 cancellation of this series, Conrad made a handful of Spanish and American films and toured with a nightclub act in Australia and Mexico City. Cast as frontier secret agent James West in The Wild Wild West (1965) in 1965, Conrad brought home $5000 a week during the series' first season and enjoyed increasing remunerations as West remained on the air until 1969. There are those who insist that Wild Wild West would have been colorless without the co-starring presence of Ross Martin, an opinion with which Conrad has always agreed. The actor's bid to star in a 1970 series based on the venerable Nick Carter pulp stories got no further than a pilot episode, while the Jack Webb-produced 1971 Robert Conrad series The D.A. was canceled after 13 episodes. When Roy Scheider pulled out of the 1972 adventure weekly Assignment: Vienna, Conrad stepped in--and was out, along with the rest of Assignment: Vienna, by June of 1973. Conrad had better luck with 1976's Baa Baa Black Sheep, aka Black Sheep Squadron, a popular series based on the World War II exploits of Major "Pappy" Boyington. Cast as a nurse on this series was Conrad's daughter Nancy, setting a precedent for nepotism that the actor practiced as late as his tenth TV series, 1989's Jesse Hawkes, wherein Conrad co-starred with his sons Christian and Shane.

Though few of his series have survived past season one, Conrad has enjoyed success as a commercial spokesman and in the role of G. Gordon Liddy (whom the actor admired) in the 1982 TV movie Will: The Autobiography of G. Gordon Liddy (1982). As can be gathered from the Liddy assignment, Conrad's politics veered towards conservatism; in 1981, he and Charlton Heston were instrumental in toppling Ed Asner and his liberal contingent from power in the Screen Actors Guild.

As virile and athletic as ever in the 1990s, Robert Conrad continued to appear in action roles both on TV and in films; he also maintained strong ties with his hometown of Chicago, and could be counted on to show up at a moment's notice as a guest on the various all-night programs of Chicago radio personality Eddie Schwartz.