We studied the effect of egg white hydrolysate (EWH) on swimming endurance in mice. 7‐week‐old male ddY mice (28–30 g) were divided into three groups and fed an AIN‐93G diet supplemented with casein ( n = 8), EWH ( n = 7), or egg white protein (EWP, n = 8) for 14 days. From day 11, the mice underwent a swimming test daily with a weight load equivalent to 10% of their body weight, and the lengths of time they swam were recorded. Blood was sampled for testing on the last day of the study. We observed that increases in the swimming duration through day 14 were significantly greater in the EWH group than in the casein group ( p = 0.049). As a factor underlying this, the hexanoyl‐lysine level in blood was confirmed to be decreased in the former group ( p = 0.013). These findings indicate that consumption of EWH extended the swimming duration and suggest the mechanistic involvement of an antifatigue effect mediated by its antioxidant activity.