Born in Passaic, New Jersey, Millie grew up in Fair Lawn, New Jersey. Her father was a merchant marine captain. Perkins was working as a receptionist at a New York City advertising agency when she caught the eye of a visiting Photographer with a resultant career as a model; by 1958 Perkins was an international cover girl. In 1958, she was vigorously pursued, and then selected, to appear in her first film, in The Diary of Anne Frank.