This study sought to determine the effects of soy–whey blended protein supplementation on sports performance and related biochemical parameters after long-term training. After a week of adaptation, eighteen 6-week-old male Wistar rats were randomly assigned to 3 groups: the standard chow diet plus whey protein (Whey) group, the standard chow diet plus soy–whey blended protein (BP) group and the standard chow diet only (control) group. Each group included 6 rats for the seven-week experiment. Before the experiment, the baseline values of body weight, grasping force and time to exhaustion due to the loaded-swimming test were recorded for each group. During the experimental period, all rats performed the loaded-swimming test until exhaustion five days each week. The results showed that the mean maximum grasping force of the BP group significantly increased between the 5^th and the 7^th week (p < 0.05) compared with the other groups. The ingestion of blended protein for 7 weeks significantly increased the mean time to exhaustion due to swimming by 1.5-fold and 1.2-fold compared with the control and Whey groups, respectively. The plasma levels of leucine, isoleucine and valine were significantly higher at 60 min after the blended protein intervention compared with the Whey and control interventions (p < 0.05). Furthermore, the ingestion of soy–whey blended protein enhanced the activities of lactate dehydrogenase and superoxide dismutase and decreased the levels of malondialdehyde in serum. These results collectively suggest that soy–whey blended protein ingestion with resistance exercise can improve sports performance and ameliorate exercise-induced fatigue in rats.