Joyce Anne DeWitt was born the second oldest of four to parents Paul and Norma DeWitt on April 23, 1949 in Wheeling, West Virginia but grew up in Indiana. Joyce began taking acting lessons when she was in high school. Although her father was hardly thrilled at his daughter's ambition, she persuaded him to let her major in theater in college. DeWitt soon moved to UCLA where she received her master's degree. After college, she worked as a legal secretary while at the same time going from audition to audition. Months passed before ABC offered her a choice of two comedy pilots but gave her only 24 hours to decide on which. After reading both scripts in a hurry, she chose the one about one guy living with two girls (Three's Company (1976)). She chose well - the other show never sold. She had been in numerous amounts of plays before but became familiar to everyone as the sensible, down-to-earth, football jersey wearing, brunette roommate Janet Wood.

DeWitt became famous and while many celebrities would automatically welcome in the huge amounts of attention, she usually kept to herself and didn't care too much for publicity.