Born in Youngstown, Ohio, as James Jonah Cummings, he moved to New Orleans when he was young. There, he worked on Mardi Gras floats and as a door-to-door salesman. He then moved to California, where he worked odd jobs before he got into voice acting.
- Cummings is the third person to voice Winnie the Pooh and Kaa, after Sterling Holloway and Hal Smith.
- He is not related to his fellow voice actors Brian Cummings or Todd Cummings.
- Jim Cummings and Brad Garrett both reprise their roles as Winnie the Pooh, Tigger, and Eeyore in the live-action Christopher Robin. This makes them the first voice actors to reprise their voice-over roles in a live-action film, followed by James Earl Jones as Mufasa in 2019's The Lion King.
- His favorite roles are Winnie The Pooh, Tigger, Darkwing Duck and Hondo Ohnaka.
- Growing up, he was a fan of Davy Crockett, he still has his coonskin cap .