Born in La Crosse, Wisconsin in 1936, Dierkop was enlisted in the US military and served in Korea after the Korean War ended. After being discharged, he enrolled in the American Foundation of Dramatic Arts in Philadelphia and pursued a career in Hollywood.

Speaking about being cast in Butch Cassidy and the Sundance Kid in 2018, Dierkop said he was suited for the part of an outlaw because his nose had been broken several times as a child. ‘My agent was on a plane reading a script and it says, Flat Nose Curry … I think I have someone in mind’ he recalled in an interview with Rob Word. ‘So I got an interview with [director] George Roy Hill and got cast, quite simply.’ Dierkop was married to Joan Addis, whom he met at the American Foundation of Dramatic Arts, from 1958 until their divorce in 1974. The former couple had two children: son Charles Jr, who died in 1990 aged 29, and daughter Lynn.