Berberis vulgaris (Zereshk in Persian) is a member of therapeutic plants in herbal medicine. There is evidence that its root contains components, such as berberine, berbamine, culumbamine and berberubine, with a relatively wide spectrum of antimicrobial activity. The aim of the present study was to examine if the plant root has any effect on the growth of broiler chickens. The plant was collected from Shiraz area in sufficient quantity and the roots were dried at room temperature and then ground into powder. One day old broiler chickens were randomly divided into seven groups (twenty chickens each) and were reared under similar conditions. The chickens received either normal diet not containing the root powder or were fed a diet containing one or two percents root powder. Chickens were weighed every five days until the age of fifty. Statistical comparison of average body weights in each group showed that chickens in group two (fed the diet containing 1% root powder from day one) were significantly (P < 0.05) heavier than the birds in the control group. It is suggested that the effect of active ingredients of the plant be examined in this respect in the future work.