Hagen gave a memorable comic performance in Singin' in the Rain as the vain, spoiled, and talentless silent film star Lina Lamont.

In 1957, Hagen co-starred in an episode of Alfred Hitchcock Presents titled "Enough Rope for Two", portraying a woman who accompanies two thieves trying to retrieve stolen money from a desert mine shaft.

[10] After appearing with Fred MacMurray in the Disney comedy The Shaggy Dog (1959), for the remainder of her career she played supporting roles, such as Marguerite LeHand, personal secretary to Franklin Delano Roosevelt, in Sunrise at Campobello (1960) and the friend of Bette Davis in Dead Ringer (1964).

Much later, in 1976, she made a comeback of sorts playing character roles in episodes of the television series Starsky and Hutch and The Streets of San Francisco.

Jean Hagen married actor Tom Seidel (who originated the role of Dr. Sanderson in the play Harvey) on June 12, 1947, in Brentwood, California.

According to Lorraine LoBianco's authoritative biography, Seidel, in his attempt to stop his wife from drinking, divorced her and gained custody of the children.

'"[12][13] Hagen died, twenty-six days after her 54th birthday, of esophageal cancer on August 29, 1977, at the Motion Picture & Television Country House and Hospital.