Charles Duncan Jr. was born in Houston, Texas, in 1926 and attended Rice University. He began his career in the Air Force, moving on to become a businessman.

Duncan served as the president of Duncan Foods Co. from 1958 to 1964 and as president of the Coca-Cola Co. from 1971 to 1974. From 1977 to 1979, he was the deputy secretary of defense. Duncan served in the cabinet of President Jimmy Carter as secretary of energy from 1979 to 1981.