It is known from partial skulls and skeletons from at least four individuals of differing biological ages, found in Tithonian (Late Jurassic) rocks of the Morrison Formation in Colorado.

Fruitadens is one of the smallest known ornithischian dinosaur, with young adults estimated at 65 to 75 cm (26 to 30 in) in length and 0.5 to 0.75 kg (1.1 to 1.7 lb) in weight.

Fruitadens is known from fossils recovered under a valid paleontological permit in the 1970s and 1980s by teams led by George Callison, for the Natural History Museum of Los Angeles County (LACM).

[7] Fruitadens is based on LACM 115747, consisting of incomplete jaws, a number of vertebrae, and partial hind limbs, of a nearly fully grown individual.

[7] Fruitadens was similar to Heterodontosaurus in anatomy, with relatively short arms and long distal sections of the legs (feet and shins).

Heterodontosaurus Lycorhinus Fruitadens Tianyulong The four individuals were found in localities at the base of the Morrison Formation's Brushy Basin Member, in crevasse splay sandstones deposited in floodplains.

The Fruita localities preserved a contemporaneous fauna including snails, clams, crayfish, various insects (represented by trace fossils), the lungfish Ceratodus, ray–finned fish, the turtle Glyptops, rhynchocephalian reptiles Eilenodon and Opisthias, several genera of lizards, a mesosuchian crocodylomorph, and the mammals Fruitafossor, Glirodon, and Priacodon.