Carroll died Nov. 16 near her home in Puerto Vallarta, Mexico, her son, Joe Krack, said.
Carroll played Garland's younger sister Agnes, who pulls a dangerous prank with the youngest sister, Tootie (Margaret O'Brien), in Meet Me in St. Louis (1944). The actress was sidelined for a few days during filming after she needed an emergency appendectomy.
Carroll then portrayed the struggling eighth-grade parish student Patsy who at first doesn't get any sympathy from Ingrid Bergman in The Bells of St. Mary's (1945).
Carroll made quite the impression as Ginger Rogers' younger sister Honeybell in Primrose Path (1940), then was loaned by RKO so she could appear on Broadway as Geraldine in Panama Hattie, a Cole Porter musical comedy about sailors in the Panama Canal Zone that starred Ethel Merman and ran from October 1940 to January 1942. (Shirley Temple had turned down the part.)
"For sunshine and sentiment, little Joan Carroll, who is now fully 8 years old, is wholly captivating," Brooks Atkinson wrote in his review for The New York Times. "She and Miss Merman get along together beautifully, and gruff old codgers are going to choke a little this Winter when tot and temptress sing 'Let's Be Buddies' and bring the house down."
Carroll also appeared opposite Ruth Warrick in two films: Obliging Young Lady (1942), in which she played the daughter of wealthy divorcing parents, and Petticoat Larceny (1943), where she was a young radio star who goes undercover to better understand her roles (and then gets kidnapped).
The Bells of St. Mary's was her last film. She continued to live in Beverly Hills, got married and then moved with her family to Colorado, her son said.
Born Joan Marie Felt in Elizabeth, N.J., Carroll and her folks came to California in 1936 when she was 5. She made her film debut in One Mile From Heaven (1937) opposite Claire Trevor and later appeared in Mr. Moto's Last Warning (1939), Basil Rathbone's Tower of London (1939), Anne of Windy Poplars (1940) and Tomorrow, the World! (1944).
Survivors include her other children Ann Marie, Mary Anne and James; her brother James; 14 grandchildren; and 19 great-grandchildren. A donation in her name may be made to Sacred Heart Jesuit Center, P.O. Box 128, Los Gatos, CA 95031.
Carroll was 85 years of age.