This study was conducted to determine the effects of diclofenac sodium in broiler chicks during the period from 20 th July /2012 to 1 st september/2012. The broiler chicks were divided into four groups A, B, C and control with ten day old bird in each. Group A was treated with @ 5mg/kg body weight, group B was treated with @ 10mg/kg body weight and Group C was treated with 20 mg/kg body weight given orally mixing with drinking water. Histopathological, hematological and biochemical tests were performed on 42 th days of age to evaluate diclofenac-induced changes between control and treated groups. Mortality rate and pathomorphological changes were observed in dead birds. The acute toxicity was assessed by observing the clinical signs and symptoms, mortality, alterations in blood biochemistry, and necropsy findings. The birds of Group A showed only mild symptoms of diarrhea and 30% mortality. In Group B, 60% and Group 70% of birds died in between 24 and 36 h post-treatment showing the symptoms of segregatory behavior, lethargy, terminal anorexia, and severe bloody diarrhea. Observation of hematological parameters like TEC, Hb, PCV and ESR on 42 th days of age showed significant (p<0.01) decrease in treatment group compare to control group. Observation of biochemical parameters (serum urea, serum creatinine) on 42 th days of age showed significantly increased (p<0.01) serum urea and serum creatinine indicating nephrotoxicity in broilers. At 12 and 24 h post-treatment this returned to the normal levels. The dead birds of the high-dose group also showed similar pattern of biochemical changes at 12 and 24 h post-treatment and revealed extensive visceral gout with characteristic histopathological lesions in liver, kidney, heart, spleen and intestine on post-mortem. The results indicate that diclofenac sodium has hepatotoxic, nephrotoxic, and visceral gout inducing potentials in broilers (cob-500), especially at higher dose.