Glandirana susurra is an endemic species of ranid frog from Sado Island in northwestern Japan. Previous phylogenetic studies indicated that this species was nested within another Japanese congeneric species, G. rugosa, which itself also contained deep intraspecific genetic variations in mainland Japan. Thus, more detailed surveys of morphological variations in G. rugosa and G. susurra are needed. In this study, I report that G. susurra differs from G. rugosa in having a thin, pale brown ring around the pupil with a relatively wide gap at its dorsal extremity, a feature which is usually absent in G. rugosa. This character exhibited no geographic variations in G. rugosa. Since this character seems to be applicable to juveniles, it can be used as an additional diagnostic character to distinguish these two parapatric species.