Born Loretta Clemens, she began her career as a pianist and singer with her brother Jack Clemens, and the siblings soon transitioned into radio, in addition to occasional film appearances in musical shorts. They had their own quarter-hour radio series which ran off and on from 1933 through 1939, and starred on the musical comedy series The Gibson Family (1934-1935; reworked as Uncle Charlie's Tent Show for the last few months), with Loretta Clemens playing Dotty Marsh. In 1936, she was a featured singer on the Philip Morris Cigarettes series Johnny Presents. During this period, she married jazz musician Frederick Tupper.
Loretta Tupper semi-retired after becoming a mother in 1942, instead teaching piano, acting, and dancing. Following her husband's death in 1975, she returned to show business, playing little old ladies in commercials (notably a series for Fruit of the Loom) and films. She had bit parts in Woody Allen's Annie Hall and The Purple Rose of Cairo, and also appeared in Something Short of Paradise (with Susan Sarandon and Marilyn Sokol), Midnight Madness (with Michael J. Fox), and The King of Comedy (with Robert De Niro and Jerry Lewis)