A longtime Brooklyn resident, Dillon died May 26 at New York's Long Island College Hospital from complications after lung surgery, publisher Scholastic Inc. announced.
Science fiction writer Harlan Ellison, a close friend, posted a note on his website that said: "Half my soul for 50 years went with him."
Leo and Diane Dillon met in 1953 at the Parsons School of Design in New York, where they were artistic rivals, and married four years later. An interracial couple, they worked on a wide range of children's projects, mastering a bold, colorful style that helped introduce kids to stories of black people worldwide. They won the Caldecott Medal for best illustration in 1976 for "Why Mosquitoes Buzz in People's Ears: A West African Folktale" and another the following year for "Ashanti to Zulu: African Traditions." No one else has been awarded the Caldecott in successive years.
The Dillons received awards as diverse as their books, including a Hugo Award for science fiction illustration and an NAACP Image Award.
"People often comment on the 'Dillon style,' " Leo Dillon said in 2000 during an interview with Locus magazine. "I think that someplace, the two of us made a pact with each other. We both decided that we would give up the essence of ourselves, that part that made the art each of us did our own. And I think that in doing that we opened the door to everything."
Born Lionel John Dillon in Brooklyn, N.Y., on March 2, 1933, he served in the Navy in the early 1950s before enrolling in art school. He and his wife worked as commercial artists before they began collaborating on book covers and story illustrations.
Their credits included book cover designs for Ellison, Ray Bradbury and other science fiction and fantasy writers and illustrations for books by Margaret Wise Brown, Madeleine L'Engle, Virginia Hamilton and Verna Aardema, author of the two Caldecott winners.
They wrote and illustrated the picture books "Rap a Tap Tap" and "Jazz on a Saturday Night" and collaborated with their son Lee Dillon, also an artist, on "Pish, Posh, Said Hieronymus Bosch."
A new work by Leo and Diane Dillon, "If Kids Ran the World," is scheduled for 2014.
Dillon is survived by his wife and his son.