Twelve species of rhinoceros beetles and chafers are reported from Biak I. and Yapen I. off the northwest coast of New Guinea; three species of Neoheteronyx are described as new. Xylotrupes clinias Schaufuss, 1885 and Engertia amboinae Brenske, 1897 are reported for the Papuan region for the first time, and the range of Lepidiota reuleauxi Brenske, 1892 is extended to the Indonesian part of New Guinea. A relationship between the scarab faunas of the Schouten and Moluccan Is. is demonstrated for the first time.