Two species of dynastine scarab beetles are reported for the first time on the island of Hawaii: the Pasadena masked chafer, Cyclocephala pasadenae (Casey) (Scarabaeidae: Dynastinae: Cyclocephalini) from North America and Temnorhynchus retusus (Fabricius) (Scarabaeidae: Dynastinae: Pentodontini) from Africa. The Pasadena masked chafer is established on the island of Hawaii, is a recognized pest of turf grass, and is a concern for agriculture and native Hawaiian arthropod species. Temnorhynchus retusus is not known to be an agricultural pest, but its spread on the islands could pose a problem for Hawaiian native species. We provide an overview of each species, characteristics for recognition of these species, and comments on their introduction to the islands.