The present study was designed to investigate the  efficacy of overdosing of vitamin D3 supplementation on growth performance, carcass parameters and some blood constituents of Japanese quail in one way analysis of variance experiment lasted in 49 days of age. Two hundred and twenty five of one day old of Japanese quail chicks were used.  The chicks were distributed into 5 treatments of 3 replicates of 15 birds each. Five levels of vitamin D3 (0, 1500, 3000, 4500 and 6000 ICU/kg diet) were used. The body weight and feed intake were recorded weekly and consequently, body weight gain and feed conversion ratio were calculated. At the end of the experiment, three birds from each group were slaughtered to evaluate carcass parts. Blood serum samples were obtained from chicks at 49 days of age after centrifuged to measure total protein, cholesterol, glucose, calcium, phosphorus and  GPT. At 49 days of age, the results showed that, the Japanese quail fed the highest level of vitamin D3 (6000 ICU/kg diet) achieved significantly (P<0.05) the highest body weight and body weight gain and the best feed conversion ratio. No  significant (P>0.05) effects due to vitamin D3 supplementation were noticed in dressed% and some blood serum parameters were measured. It was recommended that under the present experimental conditions, the overdose of vitamin D3 (6000 ICU/kg diet) achieved higher growth performance and some carcass traits of Japanese quail.