Aim: This study aimed to determine the effect of exercise training alone and in combination with coenzyme Q10 (Q10) supplementation on the Q10 level, oxidative damage, and antioxidant defense markers in blood and skeletal muscle tissue in young and aged rats. Methods: The study included 4-month old (young) and 20-month old (aged) rats. Each group was further divided into control, exercise training, Q10 supplementation, and Q10 supplementation plus exercise training groups. The exercise training program consisted of swimming for 8 weeks, and Q10 or vehicle during the same period. Results: The Q10 concentration in plasma (P < 0.05), but not in skeletal muscle (P > 0.05) increased significantly following Q10 supplementation in both the young and aged rats. Plasma SOD and CAT activity were significantly higher in the aged rats in the Q10 and Q10 plus exercise training groups than in the other groups (P < 0.05); however, there was no significant difference between the groups in skeletal muscle (P > 0.05). Additionally, plasma and skeletal GSH levels did not differ between the groups (P > 0.05). Conclusion: The present findings indicate that Q10 supplementation increased the Q10 concentration in blood but not in skeletal muscle tissue. On the other hand, Q10 administration alone and in combination with exercise challenge improved antioxidant enzyme capacity especially in the aged rats.