Summary In this study, tilapia collagen peptide (TCP) was prepared by alcalase hydrolysis of tilapia skin, and the antioxidant and hypoglycaemic effects of TCP were investigated. The results showed that TCP possessed DPPH and ABTS+ free radicals‐scavenging activities. In diabetic mice in which diabetes was induced by injection of alloxan (50 mg kg−1 bw), high‐dose TCP (1.7 g kg−1 bw) and the drug metformin (1.0 g kg−1 bw) were found to reduce 31.8% and 30.3% of blood glucose levels in 25 days, respectively. Moreover, in diabetic mice receiving high‐dose TCP, antioxidant enzymes SOD and CAT were increased by 23% and 59.2%, respectively, and MDA was decreased by 39.1%. Comparing the treated high‐dose TCP group with the metformin group, there were similar SOD (61.5 U mg−1 vs. 60.2 U mg−1) and MDA (1.4 nmol mg−1 vs. 1.3 nmol mg−1), but more (~7%) CAT (359.8 U g−1 vs. 336.1 U g−1). Together, the present data, for the first time, demonstrated that TCP possessed hypoglycaemic effects in mice.