Geronimi was born in Italy, immigrating to the United States as a young child. Geromini's earliest work in the animation field was for the J.R. Bray Studios, where he worked with Walter Lantz. Geromini left Bray in 1931 to join Walt Disney Studio, where he remained for the rest of his career. Geromini started off in the shorts department, eventually becoming a director. His 1942 short, "Lend a Paw", won the Academy Award for Best Animated Short Subject.
Geronimi moved into directing feature-length animated films after end of World War II. He was one of the directors on Cinderella, Alice in Wonderland, Peter Pan, Sleeping Beauty, Lady and the Tramp, and One Hundred and One Dalmatians.
After Geronimi left Disney in 1959, he worked in television for a number of years, including directing many episodes of the 1967 animated Spider-Man series. He retired from animation sometime in the late 1960s, and provided illustrations for children's books by Joan Pizzo.
Geronimi received the 1978 Winsor McCay Award from the International Animated Film Society, ASIFA-Hollywood, for his lifetime of contributions to the animation field. The award was presented by his long time friend and colleague Walter Lantz.
Geronimi died on April 24, 1989 at his home in Newport Beach, California. He was 87.