[6] Carradine was raised primarily by his stepmother, his father's third wife, Doris Grimshaw, and believed her to be his mother until he was introduced to Sonia Sorel at a Christmas party when he was 14 years old.

[8] He and David belonged to a musical quartet that performed in small clubs in Los Angeles and San Francisco.

He made an appearance as a killer in the Martin Scorsese film Mean Streets shooting to death the character played by his brother, David.

[8] In 1976, Carradine had the opportunity to demonstrate on screen what he considered to be his "first ambition", car racing,[7] when he played Jim Cantrell in Paul Bartel's Cannonball.

In the film Robert's character wins the cross country road race, beating the favorite, Coy "Cannonball" Buckman, played by his brother, David.

In 1978, Robert landed a demanding role in Hal Ashby's Oscar-winning Vietnam War drama, Coming Home, which starred Jane Fonda and Jon Voight.

[7] Robert was instrumental in securing his brothers David and Keith to perform with him in one of the most unusual casting arrangements in movie history.

Also in 1983, he starred in the music video for The Motels hit song "Suddenly Last Summer" as lead singer Martha Davis' love interest.

To prepare for the comedy, Carradine spent time at The University of Arizona, where the movie was filmed, participating in rush week.

In 2018, Carradine joined Andrew Cassese and Don Gibb in an interview at the Niagara Falls Comic Con.

He also appeared on his brother David's series Kung Fu as Sunny Jim, the mute companion of Serenity Johnson, played by his father John Carradine, in an episode titled Dark Angel (1972).

In 2015, he appeared on a fourth season episode of Celebrity Wife Swap with Hall of Fame wide receiver Terrell Owens.