Eastern box turtles have a wide and varied diet, consisting of insects, plants and fungi. This varied diet and tough digestive constitution allows box turtles to survive even when their favorite food sources are not available, helping to make the species successful despite its slow sexual maturity and low number of offspring.

Box turtles are not particularly fussy eaters, and they have robust digestive systems. As juveniles, their diets consist mainly of insects, including slugs and worms. As they mature, Eastern box turtles gravitate more toward plant matter as their main source of nutrition, although they still enjoy the occasional insect. Both juvenile and mature Eastern box turtles consume carrion, or dead animals, when it is available. They consume large quantities of berries, fruits and vegetable matter. The Eastern box turtle also eats mushrooms and is capable of safely digesting many mushroom species that are toxic to humans and other animals.

Those considering adopting Eastern box turtles as pets are advised to give them the same varied diet as they consume in the wild to ensure they remain happy and healthy. Otherwise, vitamin and mineral deficiencies can occur, resulting in deformities, ill health and death. It is also crucial to select a captive-bred box turtle as a pet to avoid contributing to its endangerment in the wild.