An alpheid shrimp Betaeus gelasinifer Nomura and Komai, 2000 new to Korean waters is described and illustrated based on two specimens collected from Changseun and Ulleungdo Island, Korea. This is the first record of B. gelasinifer outside Japanese waters. B. gelasinifer is readily separated from B. granulimanus Yokoya, 1927, the only member of Betaeus from Korea by the morphological differences in the first pereopods and the diaeresis of uropod. Brief note on the armature of cutting edge of the chela of the left first pereopod in Korean female specimen of B. gelasinifer is provided.