Antrodia camphorata (AC) is an endemic mushroom that grows in Taiwan. We investigated the fatigue-alleviating effects of AC on endurance capacity in swim-exercised and weight-loading mice. Male Institute of Cancer Research (ICR) strain mice from 3 groups (n = 10 per group in each test) were orally administered AC fruiting body extract for 7 days at 0, 50, and 200 mg/kg/day, designated vehicle, AC-50, and AC-200, respectively. Trend analysis revealed that AC treatments increased grip strength. AC dose-dependently increased swim time, blood glucose, and muscular and hepatic glycogen levels and dose-dependently decreased plasma lactate and ammonia levels and creatine kinase activity. The increase in swimming endurance with AC administration was caused by an increase in liver and muscle glycogen deposition. A. camphorata may have potential for use in ergogenic and antifatigue activities.