Grookey is a small, monkey-like Pokémon with a green body, a brown tail, brown, wedge-shaped ears, orange hands and feet, and an orange snout. Each of its hands has five fingers, while each of its feet has three toes. It has two large eyes with black irises and white pupils and sclerae. A lime green mask frames its eyes and, in a small bump above its snout, extends towards its forehead. Grookey has two, leaf-shaped hair tufts that hold a stick on the top of its head. Besides using it when attacking, Grookey beats this stick rhythmically against the surfaces of all sorts of objects.

This has been observed to cause grass to grow, and wilted flowers and leaves seem to regain their color when Grookey drums nearby. In the anime, it can even restore weakened plant-like Pokémon such as Bellsprout. The stick used to be a branch from a forest where troops of Grookey lived, and it has a special power due to being exposed to the energy within Grookey's body. Grookey live deep in forests. However, due to its status as a starter Pokémon, a wild Grookey is hard to come by and it is generally seen under the care of Trainers.