While collecting shore fishes from Bombay, two specimens of Blennius semifasciatus Ruppell were obtained. This species was formerly reported from Red Sea by Riippell (1835). Though Klunzinger (1870) synonymised B. semlfasciatus with Blennius cyclops Ruppell, it differs from B. cyclops in having less anal rays (5. cyclops, D.29, A.20, B. semlfasciatus, D.26, A. 18) and in other characters. Smith (1959) described B. lodosus from the south-east coast of Africa. It comes closer to B. semlfasciatus but differs from it in fin formula, supraorbital cirri and colouration. Mukerji (1935) who described B. semlfasciatus from Andaman Islands, stated that' this is perhaps one of the rarest species of the genus Blennius' (p. 273). As this is the first report from the coasts of mainland of India, a short description is given here.