Objective: Ursolic acid (UA) is a type of pentacyclic triterpenoid carboxylic acid purified from natural plants. The anti-skeletal muscle atrophy of UA is well conducted but its effect upon skeletal muscle strength via irisin is still unknown in clinical trials. The purpose of this study was to examine the effect of resistance training with/without UA on muscle strength via irisin in men. Methods: Sixteen male participants (age, 29.37 ± 5.14 years; body mass index= 27.13 ± 2.16 kg/m²) were randomly assigned to resistance training (RT, n = 7) or RT with UA (RT + UA, n = 9). Both groups completed 8 weeks of intervention consisting of 5 sets of 26 exercise, with 10~15 repetitions at 60-80% at one-repetition maximum and a 60~90-s rest interval between sets, performed 6 times/week. UA or placebo was orally ingested as 1 capsule 3 times/day for 8 weeks. The following program was measured at pre and post intervention; body weight, insulin, insulin growth like factor-1 (IGF-1), irisin, and skeletal muscle strength. Results: Body fat percentage was significantly decreased (P < 0.001) in RT + UA group, however, body weight, body mass index, lean body mass, glucose, and insulin levels were not changed. Plasma IGF-1 and irisin level were significantly increased compared with baseline levels in the RT + UA group (P < 0.05). Maximal right and left extension (P < 0.01), right flexion (P < 0.05) and left flexion (P < 0.001) were significantly increased compared with baseline levels in the RT + UA group. Conclusion: These findings suggest that elevation of serum irisin associated with skeletal muscle function can be enhanced after RT with UA.