This study was conducted to explore the effects of squid ink on growth performance, immune functions and antioxidant ability of broiler chickens during a period of six weeks. Either sex Arbor Acres broilers were equally allotted to 4 groups with 3 replicates of 20 chickens each. Broilers diets for the 4 test groups were prepared separately with starter and finisher phases. Control chickens were fed with basal diet and birds of group Exp 2, Exp 4 and Exp 6 were fed with the basal diet supplemented with 2%, 4% and 6% of squid ink, respectively. Broilers were sacrificed to investigate antioxidant parameters of sera, indices of thymus, spleen and bursa of fabricius and spleen lymphocyte proliferation, as well as growth performance on the $21^{th}$ and $42^{th}$ day. The results revealed that, i) squid ink promoted growth performance of broilers during days 22 to 42 and the whole trial period (p<0.05 or p<0.01); ii) squid ink elevated relative weight of the three immune organs during the starter phase and spleen lymphocyte proliferation throughout the experiment (p<0.05); iii) squid ink increased SOD activity and decreased MDA level in sera from broilers during the whole period (p<0.05). The above results suggest that squid ink could improve growth performance, antioxidant ability and immune functions of growing broiler chickens and be employed in the development of feed additives for animals.