Species richness, abundance, and seasonal distribution of Coleoptera Scarabaeoidea were evaluated in a deciduous tropical forest at Choix and El Fuerte, Sinaloa, Mexico, from July to October 2009 by means of nocturnal collections at three locations. More than 36,000 specimens were obtained, representing 45 species and 21 genera of Melolonthinae, Rutelinae, Dynastinae, Scarabaeinae, Hybosoridae, Ochodaeidae, Geotrupidae, Trogidae, and Passalidae. The genus with the highest richness index was Phyllophaga with 12 species, Phyllophaga opaca being the dominant species. The best represented species were Oxygrylius ruginasus (96.97%), Digitonthophagus gazella (1.18%), Cyclocephala freudei (0.34%), Pelidnota virescens (0.13%), and Phyllophaga opaca (0.04%). Adult activities were strictly seasonal, because the greatest abundance occurred during August (89.91%), where high rains were recorded, while during October no scarab beetle was collected.