This study investigated the impact of an essential oil (EO) mixture (Biomin) on growth performance, carcass yield, visceral organ weights, and duodenal crypt depth in native Turkish geese (Anser anser). Sixty 1-day-old goslings constituted the animal material of the trial. Goslings were divided into three treatment groups, each consisting of four subgroups having five animals each. Animals were homogenously distributed among the groups after being weighed and identified. The three treatment groups received the essential oil mixture at rates of 0.0% (without EO), 0.1% and 0.2%, respectively. The animals were given concentrate feed (21.93% CP and 3010 kcal/kg ME) for the first 2 weeks, and were both grazed and provided with barley meal for the next 8 weeks. The trial was continued for a period of 10 weeks. Results showed that the essential oil mixture had no significant effect on live weight gain, feed intake, feed conversion rate, carcass yield, and heart-liver-gizzard weights (P>0.05). On the other hand, the crypt depths of the EO 0.1% and EO 0.2% groups were greater than that of the EO 0.0% group (P<0.05). This study demonstrated that EO supplementation had no impact on performance, but increased duodenal crypt depth in native Turkish geese.