The father was a painter, and her mother, who was likely to become a successful concert pianist, resigned to her career in favour of her family.

After being trained at Helmut Kraus's Drama School, Erni Mangold performed from 1946 to 1956 at Vienna's Theater in der Josefstadt.

From 1972, she worked at Salzburg Mozarteum, later she taught in the Helmut Kraus's Drama School and at the Max Reinhardt Seminar, and from 1984 to 1995, she was professor at University of Music and Performing Arts, Vienna.

Among her roles in international film productions is a short but memorable turn as a palm reader in Richard Linklater's Before Sunrise (1995).

In 2011, she published her memoirs, titled Lassen Sie mich in Ruhe which is translated colloquially as "Get off my back!".