Buergeria japonica (Rhacophoridae) thrives in diverse habitats, from montane forests to the mouths of small rivers opening onto sandy beaches. The osmoregulatory system of B. japonica may differ between populations living in these contrasting environments. In this study, we compared the activity of cutaneous Na⁺/K⁺-ATPase in two populations of B. japonica from different habitats (montane vs. coastal). Our results reveal a significant difference between the Na⁺/K⁺-ATPase activity of the two populations of B. japonica, with the coastal population having higher Na⁺/K⁺-ATPase activity. Because the Na⁺/K⁺-ATPase plays a crucial role in osmoregulation in high salinity, these results are consistent with the higher salinity tolerance of the coastal population. It is not known whether the difference in Na⁺/K⁺-ATPase activity between populations is a result of local adaptation or phenotypic plasticity. More detailed work will be needed to disentangle the patterns of differentiation in physiological responses to salt in these amphibians.