The aim of the present study was to investigate the effect of dietary supplementation with an essential oil mixture, a commercially available organic acid and a probiotic on growth performance and carcass yield of broilers. One thousand two hundred and fifty sexed one day-old broiler chicks were randomly divided into five treatment groups of 250 birds each (negative control, organic acid, probiotic and essential oil mixture (EOM) at two levels). Each treatment group was further sub-divided into five replicates of 50 birds (25 male and 25 female) per replicate. The oil in the EOM was extracted from different herbs growing in Turkey. An organic acid at 2.5 g/kg diet, a probiotic at 1 g/kg diet and the EOM at 36 mg and 48 mg/kg diet were added to the basal diet of the birds. There were significant effects of dietary treatments on body weight gain, feed intake, carcass yield and intestinal weight of the broiler at 42 days of age. At day 42, birds fed the diet containing 36 mg EOM/kg showed the highest body weight gain. This was followed by chicks on the diet containing 48 mg EOM/kg, the probiotic, the organic acid and the negative control, in descending order. The addition of the essential oil mixture to the diet improved the feed conversion ratio significantly as compared to the negative control and the organic acid treatment. The feed intakes at days 21 and 42 were significantly different between the treatments. The addition of 48 mg EOM/kg increased carcass yield significantly above the other treatments, while the addition of EOM and the organic acid reduced the intestinal weight significantly. It was concluded that the supplementation of the herbal essential oil mixture to broiler diet had beneficial effects on body weight gain, feed conversion ratio and carcass yield.