This study was conducted to investigate the effects of dietary supplementation of garlic by-products on performance, proximate composition, carcass characteristic, cholesterol, and blood composition of chickens. Broiler chicks were fed diets for 5 weeks with a diet 1% garlic by-product (T1), 2% garlic by-product (T2), and 5% garlic by-product (T3). There were no difference among diet in performance. In proximate composition, crude fat of chicken meat was decreased in diets by addition of garlic by-product than control, but moisture and crude ash were no significant difference. Liver weight was significantly increased (P<0.05) by the dietary supplementation with garlic by-products compared to the control diet. The total cholesterol and LDL-cholesterol of treatment groups was lower than control, and the HDL-cholesterol of treatment groups was higher than control (P<0.05). Especially, T3 was significantly (P<0.05) more effective in improving cholesterol compared to other treatment groups. In blood composition, GOT of broiler was decreased in diet by garlic by-products than control group, but GPT, triglyceride, and glucose were no significantly different. In conclusion, these data indicate that supplementation of garlic by-products (T3) were most effective in decreasing total cholesterol, LDL-cholesterol, and GOT and increasing HDL-cholesterol.