Determining the influence of a sublethal concentration of the organophosphate pesticide profenofos on the proximate composition of muscle in Catla catla, Labeo rohita, and Cirrhinus mrigala was the aim of this study. Three sublethal concentrations of profenofos were given to the fish in three replicates for eight weeks. Moisture content exhibited a rapid increase in C. catla, L. rohita, and C. mrigala, with an increase in the dose of profenofos. Decreases in protein, fat, and carbohydrate contents were recorded against different sublethal doses of profenofos in C. catla, L. rohita, and C. mrigala compared to control fish. Ash contents exhibited no proper order of an increase or decrease in these fish species against the exposure of different doses of profenofos. It has been concluded that the maximum allowable toxicant concentration (MATC) endpoints for protein, fat, ash, and carbohydrate were more sensitive and may be successfully used as a new biomarker for monitoring early changes induced by pesticides. The findings of this study may be helpful for monitoring and regulatory agencies to develop a strategy against these important pollutants.