ABSTRACT. – Our knowledge on the biology and ecology of black snoek Thyrsitoides marleyi Fowler, 1929 is highly limited, since most of the available literatures on this species are taxonomic accounts or first reports. The present study provides the first report of T. marleyi in the Andaman and Nicobar Islands waters, India. Detailed taxonomic account of the species using traditional as well as molecular (COI DNA barcoding) methodologies and morphology of sagittal otolith and brain are presented and discussed. Further, information on the biology of this sporadically reported species is described based on specimens caught during longline survey for swordfish. Overall sex ratio is skewed to males (1:4.6, F:M) and the size at maturity (TL50) estimated is 101.1 cm (males) and 106.7 cm (females). Average absolute fecundity is 0.93 million ova, while the relative fecundity is 216.84 eggs per gram of body weight. Trophic level estimated was 4.15 and mesopelagic teleosts, predominantly of the family Myctophidae and other groups of the deep scattering layer forms bulk of black snoek diet.