A non-ovigerous female of Nerocila japonica Schioedte and Meinert, 1881, was found to parasitize the pectoral fin of a yellowfin goby, Acanthogobius flavimanus (Temminck and Schlegel, 1845) (Gobi- idae), caught in a brackish water region of the Yabi River, which empties into the Sea of Japan, at Dogo Island, one of the Oki Islands, Okino-shima, Shimane Prefecture, western Japan. This represents the second record of N. japonica from the prefecture. Based on the previous and present records, the yellowfin goby is regarded as one of the important hosts for N. japonica. This paper also reviews the occurrence of N. japonica in brackish waters. The species infects euryhaline fish – es, such as the yellowfin goby and the big-scaled red – fin, Tribolodon hakonensis (Günther, 1877) (Cyprini- dae), as well as coastal marine fishes, and is found on those euryhaline fishes in brackish waters.