The antioxidant and anti-aging activities of a sleep-promoting peptide from bovine milk were evaluated in this study. Four in vitro methods, namely 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), hydroxyl, and superoxide anion radical scavenging assays, were used to evaluate its antioxidant activity. Caenorhabditis elegans was used as a model organism to evaluate its anti-oxidant and anti-stress capacity in vivo. The results showed that the peptide scavenged 44.27% of DPPH, 18.37% of superoxide anion, 37.22% of hydroxyl radical and 24.83% of ABTS radical at 0.1 mg/mL. In addition, the sleep-promoting peptide obviously extended the life span of Caenorhabditis elegans, protected against oxidative stress and heat stress, improved the mobility of Caenorhabditis elegans without damaging its reproductive ability, significantly increased the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and significantly reduced malondialdehyde (MDA) content (P < 0.05, P < 0.01). In conclusion, the sleep-promoting peptide has good antioxidant and anti-stress effects both in vivo and in vitro, and thus shows promise for wide application.