The anti-fatigue effect was investigated of the probiotic supplement, OM-X®, on forced swimming capacity in mice. Mice were administered either vehicle (distilled water; DW) or OM-X® (85 mg/kg body weight) by gavage for 4 weeks. Forced swimming tests were conducted weekly using the Ishihara-modified Matsumoto swimming pool. The endurance swimming time of the final forced swimming exercise in mice fed with OM-X® group showed an approximately 2-fold increase compared with the vehicle control group. Biomedical parameters, including blood lactate, blood superoxide dismutase (SOD) activity, serum triacylglycerol (TG), hepatic total lipids (TL), TG and phospholipid (PL) were significantly lower in mice fed-with OM-X® than those in the vehicle control group. Furthermore, the mRNA expression levels of carbamoyl phosphate synthetase 1 (Cpsl) and arginase I (Argl), in the urea cycle, were increased by OM-X® feeding. Thus, our findings suggest promotion of lipid metabolism and up-regulation of the urea cycle, at least in part, for the anti-fatigue effect mediated by OM-X®.