The present study was carried out to determine the 96-hour LC₅₀ value of the herbicide Isoproturon in the freshwater fish Cyprinus carpio. Acute toxicity experiments were conducted following standard APHA procedures, and the LC₅₀ value was calculated using Probit analysis. Healthy fish were acclimatized to laboratory conditions for a period of 30 days before the commencement of the experiment. During acclimatization, suitable water quality parameters such as temperature, pH, and dissolved oxygen were maintained under controlled conditions. A stock solution of Isoproturon was prepared, and different groups of fish were exposed to varying concentrations of the herbicide for 96 hours under semi-static conditions. Throughout the exposure period, several behavioral changes were noticed in the treated fish, including erratic swimming movements, increased mucus secretion, loss of equilibrium, frequent surfacing activity, and reduced feeding behavior. These abnormalities became more prominent with increasing concentration and duration of exposure.