Derr graduated from Norristown High School in 1933. While he worked as a bank clerk, he acted with a little theater group in Norristown, Pennsylvania.
Beginning in the 1950s, most of Derr's work was done on television. In 1959, he was the host of Fanfare, a summer dramatic anthology series on NBC-TV.
On the screen, Derr was primarily a character actor. He had a starring role in a 1951 science-fiction film, When Worlds Collide. Derr starred in Invisible Avenger (1958). The film about The Shadow was the basis for two television pilot episodes, neither of which was developed into a series.
A life member of The Actors Studio, Derr landed the majority of his leading roles on stage. In 1955, he sang in the lead role in the Broadway musical Plain and Fancy. His other Broadway credits include Invitation to a March (1960), Maybe Tuesday (1957), A Phoenix Too Frequent (1949), and The Closing Door (1949).
In 1965, he played the role of Dr. Dwyer in the three-part serial, "The Adventures of Gallegher," on Walt Disney's Wonderful World of Color, and later made appearances in Barnaby Jones and the 1976 miniseries Rich Man, Poor Man Book II.
On May 8, 1992, Derr died of pancreatic cancer in Santa Monica, California.
