Abstract <p>Hilsa shad (<i>Tenualosa ilisha</i>), is one of the most prominent anadromous species throughout South Asian countries due to both commercial and social values. Despite its high value, fundamental biological features like sexual differentiation have yet to come to a consensus. Hence, based on a detailed histological examination using gonad tissues, <i>T. ilisha</i> is validated as a protandrous hermaphroditic species. The study is carried out in six localities from marine, estuarine and riverine habitats within Bangladesh territory. From histological analysis, seven individuals are confirmed with clinical features of transitional stages out of 203 individuals. The total length of females is significantly greater than that of males, while hermaphrodites are identified with a total length of ~28 cm. The gonads of hermaphrodites are mainly observed with two successive stages, termed early (oocytes with spermatids, spermatozoa, or degenerating spermatozoa) and late (oocytes with spermatocyte). Surprisingly, evidence of hermaphroditism is found predominantly within marine habitats and no transitional feature has been detected in any of the riverine individuals. From here, we would like to assume that the transformation starts before entering fresh water and becomes obvious after completing at least one back and forth journey.</p>