The histopathological changes are observed in the muscle tissue of the fresh water fish Clarias batrachus exposed to different concentrations of untreated and treated sago effluent. The concentration chosen for untreated effluent and treated effluent were 50% and 100%. The histology of muscle tissue showed various degrees of deterioration when compared to control. The deterioration was very much reduced in the treated sago effluent when compared to the untreated sago effluent.