The impact of a fish sanctuary on fisheries diversity was studied for two years in Chalan Beel, Tarash Upazila, Sirajganj district, where the sanctuary was established at the end of the first year. Seine net (Berjal) was used to collect data on a monthly basis. There were 42 species recorded from 8 orders and 18 families, including two exotic species, Cyprinus carpiro and Oreochromis mossambicus. Puntius puntio was the most common species (18.38%), followed by Colisa fasciata (9.73%) and Chanda nama (9.28%). The order Cypriniformes (16 species) was discovered to be the dominant order, accounting for 47.78% of the total order, followed by Perciformes (22.85%) and Siluriformes (21.40%). The Shannon-Weaver diversity index (H) ranged between 2.26 and 2.66. The average value was higher (2.53) after the sanctuary was established than before (2.39). The impact of the fish sanctuary may have resulted in an increase in the biodiversity index and total catch. As a result, sanctuary establishment can be expanded to address the gradual improvement of fisheries diversity. J Bio-Sci. 30(1): 61-68, 2022 (June)