Soil salinity has emerged as one of the most prominent threats to modern intensive farming systems, and it has necessitated the cultivation of halophytes to ensure food security and human nutrition.Peucedanum japonicumThunb. is an edible wild plant with medicinal value that is widely distributed along the Pacific coast of western Japan. However, the adaptive mechanisms of this plant with respect to salt stress tolerance have not yet to be elucidated. The purpose of this study was to compare the physiological responses ofP. japonicumto salt stress with those of barley (Hordeum vulgare), which is considered a salinity-tolerant plant. Seedlings of both species at the same height were exposed to different concentrations (0, 50, 75, and 150 mM) of NaCl for 16 days, after which the leaves were analyzed with respect to different physiological parameters. The results revealed a maintenance of leaf growth inP. japonicumcompared with that in barley, the growth of which was severely impaired at low concentrations of NaCl (50 and 75 mM). In response to salt stress, a higher suppression of Na(+)and Cl(-)assimilations was observed inP. japonicumthan in barley under all NaCl treatments. Moreover, P. japonicum showed a greater ability to maintain leaf K(+)and Ca(2+)concentrations, whereas barley exhibited a significant reduction in the concentrations of these ions under saline conditions. Thus, the superior salinity tolerance ofP. japonicumcould be attributed to a more efficient maintenance of ionic balances. Taken together, our results indicate thatP. japonicummay be classified as a halophyte, given its superior regulation of K+, Ca2+, SO4-, and sucrose concentrations and lower NO(3)(-)concentrations compared with those of barley.