The son of Chicago Cubs baseball player William S. Hart,[2] he attended the University of Pittsburgh[3] and worked as a clothing salesman before pursuing an acting career.

After signing with Columbia Pictures in 1939, he changed his name to Robert Sterling to avoid confusion with silent western star William S.

[4] Sterling appeared in small parts for Columbia movies, often uncredited: Blondie Meets the Boss (1939), Romance of the Redwoods (1939), First Offenders (1939), Outside These Walls (1939), The Chump Takes a Bump (1939), That Girl from College (1939), and a serial Mandrake the Magician (1939).

Sterling was in Good Girls Go to Paris (1939), The Man They Could Not Hang (1939), Golden Boy (1939), The Gates of Alcatraz (1939), A Woman Is the Judge (1939), The Story of Charles Goodyear (1939), Scandal Sheet (1939), Mr Smith Goes to Washington (1939), Beware Spooks!

(1939), Blondie Brings Up Baby (1939), The Amazing Mr Williams (1939), Glove Slingers (1939), The Awful Goof (1939) (a short), and Crime's End (1939).

[6] Sterling served in World War II as a United States Army Air Corps flight instructor.

He made an independent Western, The Sundowners (1950) with Robert Preston and John Drew Barrymore, and did Bunco Squad (1951) at RKO.

Sterling had an excellent part as Steve Baker, opposite Ava Gardner as Julie, in the hit MGM 1951 film version of Show Boat.

On December 18, 1957, Sterling and Jeffreys played a couple with an unusual courtship arrangement in "The Julie Gage Story" on the first season of NBC's Wagon Train.

He had good roles in Return to Peyton Place (1961), as Mike Rossi, husband of Eleanor Parker, and Voyage to the Bottom of the Sea (1961) for Irwin Allen.

[13] In the 1970s Sterling was a vice president and the spokesman for a company that implemented the software for one of the first supermarket barcoding and computer inventory systems.

[3] Sterling met actress-singer Anne Jeffreys soon after his Broadway debut, and they wed in 1951 and remained married for 55 years until his death.