Born Ralph Pierre LaCock in Clarksburg, he grew up in Wheeling, Huntington, and later New York City—the sister of future film actress Joanne Dru. By age 15, he was touring as a singer and later changed his name to Peter Marshall. He returned to Huntington to finish high school before serving in World War II.

After the war, he worked in radio, formed a comedy duo, and appeared in movies, Broadway shows, and TV series. In 1966, he became the host of The Hollywood Squares, a job that lasted 16 years and earned him four Emmy Awards.

Marshall kept performing and was inducted into the West Virginia Music Hall of Fame in 2013.