Dumont played wealthy aristocratic widows who Groucho alternately insulted and romanced for their money. They include Mrs. Rittenhouse from Animal Crackers and Mrs. Claypool from A Night at the Opera.

Over the course of her lifetime she played in 40 movies, not including some minor silent work. Her first feature film was the Marx Brothers movie The Cocoanuts in 1929 in which she played Mrs. Potter, the same role she played in the stage version from which the film was adapted. Her last movie was What a Way to Go! in 1964.

She also played the same type with W.C. Fields (in Never Give a Sucker an Even Break), Abbott and Costello, Laurel and Hardy, Jack Benny and Danny Kaye. She also played some dramatic parts.