Earthworm Jim 3D is a platform game, the third in the Earthworm Jim series. It is a sequel to Earthworm Jim and Earthworm Jim 2, and the first game in the series to not be developed by Shiny Entertainment, which had recently instituted a strict "no sequels" policy.

Earthworm Jim is hit by a flying cow that sends him into a coma. Jim awakens within his own subconscious and discovers he has gone insane. His past villains have entered his subconscious and if something doesn't happen soon, Jim will be in the coma forever. His super ego has been unleashed within his subconscious to stop the madness. To restore his sanity he must find the Golden Udders of lucidity. When Jim enters his subconscious, he finds out that his four mind chambers have been taken over by his worst fears. He must collect Golden Udders to unlock the other three chambers and Green Marbles to unlock the levels within the chamber. Jim defeats four villains who took over his mind chambers, and finally faces the personification of his trauma: Earthworm Kim.