Green sunfish are omnivores, which means they consume both plant and animal matter. They readily eat insects, larvae, zooplankton, eggs, snails, crawfish, and other small forage fish.

Its diet can include aquatic insects and larvae, insects that fall into the water, crayfish, snails, other molluscs, turtle food, frogs, some small fish, fish eggs, bryozoans, zooplankton, other small invertebrates, and sometimes plant material. They are omnivores.

In the wild, green sunfish will eat crayfish, small fish, and insects. This makes them naturally carnivorous, and in captivity, you will need to feed them crickets and bloodworms a couple of times per week. They will take a little time to adjust to a diet primarily consisting of pellets or food flakes.