Sundarbans, the largest mangrove forest of the world is located in Bangladesh and India. Studies done on the diversity of fish fauna in the Sundarbans mangrove forest of Bangladesh are sparse and patchy. Here we take the opportunity to provide an updated checklist of the fishes of the Sundarbans, Bangladesh based on primary and secondary data. Field surveys were undertaken in the aquatic habitat of Sundarbans core area along with its adjacent marine habitat from June 2015 to July 2017. Based on published information and primary observations the updated list of fishes covers a total of 322 species belonging to 217 genera, 96 families, and 22 orders. Additionally, four species of fishes, are newly reported in Bangladesh waters, viz., Mustelus mosis Hemprich & Ehrenberg, 1899; Lagocephalus guentheri Miranda Ribeiro, 1915; Carangoides hedlandensis Whitley, 1934; Uranoscopus cognatus Cantor, 1849. The global IUCN Red List status of each species has been enlisted. The updated checklist will constitute the reference inventory of fish biodiversity for the Sundarbans, a natural world heritage site.