Examining how species use and partition resources within an environment can lead to a better understanding of community assembly and diversity. The rich early Late Miocene (early Vallesian) deposits at Rudab\ anya II (R. II) in northern central Hungary preserve an abundance of forest dwelling taxa, including the hominoid Rudapithecus hungaricus. Here we use the carbon and oxygen stable isotope compositions of tooth enamel carbonate from 10 genera of medium to large-bodied mammals to evaluate resource use and partitioning among the herbivore community, and to reconstruct the paleoenvironment of Rudapithecus. The range of stable carbon and oxygen isotope values (δ13CE and δ18OE) displayed by the R. II fauna indicates a variable forest environment, which included both open and closed canopy habitats. The relatively low δ13CE and δ18OE values found in all sampled taxa are consistent with high levels of precipitation and humidity. Significant differences in stable isotope values were observed among the sampled fauna, supporting the interpretation of resource specialization and partitioning. Higher δ13CE values found in Aceratherium incisivum (Rhinocerotidae), Lucentia aff. pierensis (Cervidae), Hippotherium intrans (Equidae), Tetralophodon longirostris (Gomphotheriidae), Propotamochoerus palaeochoerus and Parachleuastochoerus kretzoii (Suidae) suggest foraging in more open canopy habitats, while lower δ13CE values found in Miotragocerus sp. (Bovidae), Dorcatherium naui (Tragulidae), and Micromeryx flourensianus (Moschidae) imply a preference for more densely canopied habitats. Several of the sampled taxa yielded relatively higher δ18OE and δ13CE values indicative of fruit consumption, including the small ruminants, cervid, and bovid. The analyzed isotope values reflect a moderate degree of dietary niche overlap between taxa. An abundance of plant resources likely allowed for the coexistence of this diverse community of predominantly browsing herbivores. Within the gradient of more open to closed canopy forest, it is likely that Rudapithecus occupied dense closed canopy habitats where access to fruit was relatively continuous. The progressive fragmentation and replacement of humid forests by more open and seasonal woodlands during the late Vallesian would have had a significant influence on the extinction of this fossil ape.