Ecological interactions are especially challenging to study in the deep-sea where direct observation is limited and specimens in museum collections are the most accessible source of information.  The glowbellies in the genus Acropoma are bioluminescent, mesopelagic fish that inhabit deep waters between 50 m and 500 m off Korea, Japan, Indonesia, and Thailand. Two species of Acropoma, A. hanedai and A. japonicum, co-occur and are caught together during fisheries operations in the waters off southwestern Taiwan. This provided a rare opportunity to explore if closely related species in the same deep-sea habitat exhibited dietary niche partitioning. We examined stomach contents using specimens collected incidentally in fisheries operations off of Donggang, Taiwan in February and May and in the ichthyological collection of the Bell Museum of Natural History. Acropoma hanedai more commonly had crustacean stomach contents in February and fish in May, with the opposite pattern in A. japonicum. Larger fish statistically were more likely to have fish prey in the stomach in both species. However, the seasonally different dietary preference between species remained statistically significant even when accounting for the stomach-contents effects of size of fish. This work is one of relatively few studies of niche partitioning in the deep sea.