Usage of antibiotic growth promoter is eliminated for the poultry production starting from January 2018. This policy may affect animal performance and health status in tropical countries like Indonesia. A study of Chitosan Oligosaccharide (COS) and L-arginine supplementation was carried out to evaluate the growth performance of broiler. A total of 300 DOCs (day old chickens) broilers with an initial average body weight of 46 g, were randomly treated into 5 treatments with 6 replications (10 unsexed birds in each pen) for 35 days. Dietary treatments were (P0) basal diet (BD) without supplement, (P1)BD + Antibiotic growth promoter (Zinc Bacitracine 200 mg kg−1) of diet, (P2) BD + COS 100 mg kg−1 of diet, (P3 ) BD + L-arginine 1.9% of diet, (P4) BD + COS mg kg−1 + L-arginine 1.9% of diet. The results showed that treatments with COS and L-arginine significantly (P <0.05) increased feed intake, body weight, weight gain and reduce feed conversion ratio at starter period compared with fed P0. Furthermore, feed conversion ratio and mortality were significantly (P <0.05) decreases at all treatments and body weight and weight gain significantly (P <0.05) increased only at COS treatment compared with fed P0, at the overall experimental periods. In conclusion, dietary addition of COS 100 mg kg-1 is able to use as alternative for antibiotic growth promotor replacement without giving effect on broiler performance