This study investigated the effects of various stocking densities on the growth performance of Korean native ducks. Twelve hundred day-old ducklings were reared for 50 days in a duck house (windowless, plastic wire-floor pen). Two weeks later, 852 of these ducks (350±30 g) were selected for at least 80% uniformity per stocking treatment (six treatments, four replications/treatment, depending on a stocking density of 4~9 birds m<sup>−2</sup>). Experimental diets were corn-soybean-based and broiler ducks were grouped based on age [0~21 days of age (CP 21%, ME 2,900 kcal/kg) and 21~50 days of age (CP 17%, ME 3,100 kcal/kg)]. Body weight (BW) did not significantly differ among different aged treatment groups (<italic>P</italic>>0.05); however, uniformity decreased with higher stocking densities (<italic>P</italic><0.05). Feed intake and feed conversion ratio of ducks aged 42~50 days significantly decreased in the T4-6 treatments compared with the T1-3 treatments (<italic>P</italic><0.05). In all experimental periods, BW gain was not significantly different among treatments, but feed intake decreased significantly as the stocking density increased (<italic>P</italic><0.05), and feed conversion ratio was significantly different among six treatments with stocking density (<italic>P</italic><0.05). In conclusion, we found that the stocking density of Korean native ducks in a plastic wire-floor pen was approximately 7 birds m<sup>−2</sup> in consideration of productivity and uniformity.