A rare parasitic copepod, Boylea longispica Cressey, 1977 (Poecilostomatoida, Bomolochidae), was redescribed based on a specimen collected from a rainbow runner, Elagatis bipinnulata (Quoy & Gaimard, 1825), caught in a set net installed off Tai-Dong, Taiwan. This is the second recording of the parasite since its original report in 1977 from Thailand and Caroline Islands. In Taiwan, B. longispica was found on one occasion only in our past ten years of survey of parasitic copepods throughout Taiwan. A key is provided to 19 genera of the Bomolochidae.