Channa punctatus is one of the edible fishes consumed by the local people of Jaipur city, from the water bodies around the city. Endosulfan not only changes the physico-chemical characteristics of water but also impose drastic impact on the fish. Therefore, the present work was undertaken to study the behavioural alterations and biochemical changes in muscles of the freshwater fish Channa punctatus caused by sub-chronic exposure to the organo-chloride pesticide endosulfan. The sub-chronic exposure of muscles to endosulfan at three sub-lethal concentrations 0.006 ppm (Group II), 0.01 ppm (Group III) and 0.02 ppm (Group IV) for 15 days showed significant reduction in total proteins, cholesterol, glycogen and total lipids. Group I served as control. The effects were both time and dose dependent. Results also revealed that normal behaviour of the fish was adversely influenced by endosulfan treatment as noted by decreased swimming activity and an increase in surfacing frequency, opercular movements and mucus secretion. This study reflects on the behavioral and biochemical changes and also highlights the changes in physiological functions of fish living in polluted waters. It can be concluded that endosulfan not only lowers the major metabolic constituents but also lowers the nutritive value of the fish.