Spatial separation and dietary differences may allow the coexistence of similar sized ungulate species. Over the past two decades, populations of the sika deer (Cervus nippon) have increased markedly and overlapped with the habitats of the Japanese serow (Capricornis crispus). Recently, the Japanese serow population has declined and shifted its habitat from higher to lower altitudes in Shikoku, Japan. To examine the potential for the coexistence between the Japanese serow and the sika deer, seasonal dietary and habitat overlaps were investigated in a warm temperate area in Shikoku. Although fecal analyses showed a high dietary overlap between the Japanese serow and the sika deer, the camera trap results revealed the differences in habitat uses between the two species: the Japanese serow utilized steep rocky slopes, whereas the sika deer appeared more frequently in grasslands. Artificially created grasslands on the present study area would contribute to the difference of habitat utilization between the two species.