Una Merkel began her film career as a stand-in for Lillian Gish in the silent film 1920., Although it remained initially not in the film, but moved to New York City to play on Broadway theater. There she gave in February 1923 her debut with Two by Two. 1930, noted the success with a Girl Crazy.
According to Hollywood, she came again until 1930 and then played numerous, mostly comic supporting roles. One of her most famous performances they had in 1939 in the comedy Western Destry Rides Again by Saloonrauferei with Marlene Dietrich. In 1962, she received an Oscar nomination for her role in Summer and Smoke by Peter Glenville.
From the 1950s, Merkel turned back to the stage and had strengthened again particularly in The Ponder Heart by Eudora Welty success.