Males of the nematode Philometra lateolabracis (Yamaguti, 1935), the type species of the genus Philometra Costa, 1845, were discovered for the first time in gonads of its type host, the Japanese seaperch, Lateolabrax japonicus (Cuvier). Morphological comparisons carried out between the collected male and female P. lateolabracis with the male and female philometrid nematodes previously reported as P. lateolabracis infecting chicken grunt, Parapristipoma trilineatum (Thunberg), and red sea bream, Pagrus major (Temminck et Schlegel), revealed that the latter represent two new species, Philometra isaki sp. n. and Philometra madai sp. n., respectively. Molecular comparison of ITS2 rDNA between P. lateolabracis and P. madai supported the morphological conclusion that the two nematodes obtained from different fish species should be assigned to different species.