Abstract: The current study was designed to determine the genotoxic effect of endosulfan at sublethal concentrations (66, 50 and 33% of LC50, 1.5 μg L–1) in peripheral blood erythrocytes of an economically important indigenous Indian major carp Mori, Cirrhinus mrigala . A total of 180 fish were divided into four groups, each group received 45 individuals. Group 1st served as control (received no endosulfan), while group 2nd (0.5 μg L–1), 3rd (0.75 μg L–1) and 4th (1 μg L–1) were exposed to endosulfan. For investigating the induced DNA damage, the blood samples were collected from the caudal veins of the fingerlings in all the groups after 7, 14, 21 and 28 days of endosulfan exposure. Endosulfan induced DNA damage in all the treated groups at all concentrations, in terms of percentage of damaged cell (% damage cell) and Genetic Damage Index (GDI) based on visual classification of the extent of damage (Class 0-4) and cumulative tail length (μm). A concentration and time dependent increase was observed in DNA damage in the exposed groups, the highest damage was observed in group 4th (1 μg L–1) followed by group 3rd (0.75 μg L–1). Similarly, the highest level of DNA damage was observed in peripheral blood erythrocytes sampled after 28 days, followed by 21 days after exposure. The current study displayed the severe genotoxic potential of endosulfan in Cirrhinus mrigala , even at sublethal concentrations. Therefore, the indiscriminate and injudicious use of endosulfan should be strictly monitored and banned or at least controlled by the responsible governmental authorities.