This study was conducted to evaluate the effects of dietary onion supplementation on the growth rate and blood cholesterol level in finishing pigs. Sixty $Duroc;{ imes};Yorkshire;{ imes};Landrace$ pigs ($69.75{pm}0.79kg$ average BW) were used in a 50 day growth assay. Dietary treatments included 1) corn-SBM (Con), 2) 1)+dietary onion rice bran 1.0% (ORB1), 3) 1)+dietary onion rice bran 2.0% (ORB2). For overall period, average daily weight gain and average daily feed intake were increased by the addition of dietary onion compared with Con (linear effect; p<0.01). Feed efficiency ratio was successfully improved by supplementation of dietary onion (linear effect; p<0.01). The total cholesterol concentrations in serum decreased as the concentration of onion in the diets was increased (linear effect, p<0.06). Also, LDL-cholesterol concentrations in serum tended to decrease in pigs fed onion than in those fed Con diet group (linear effect, p<0.04; quadratic effect, p<0.09). The HDL-cholesterol and triacylglyceride concentrations in serum were not influenced by the onion supplementation. The results obtained from this feeding trial suggest that the dietary onion supplementation for finishing pigs weighed 70 to 108 kg had improved growth performance and reduced total cholesterol level of serum.