Oxidative stress, decreased antioxidant capacity, and impaired sperm mitochondrial function are the main factors contributing to male infertility. The goal of the present study was to assess the effect of the per os treatment with Carni-Q-Nol (440 mg L-carnitine fumarate + 30 mg ubiquinol + 75 IU vitamin E + 12 mg vitamin C in each softsule) in infertile men on sperm parameters, concentration of antioxidants (coenzyme Q10, CoQ(10-TOTAL), γ, and α-tocopherols), and oxidative stress in blood plasma and seminal fluid. Forty infertile men were supplemented daily with two or three Carni-Q-Nol softsules. After 3 and 6 months of treatment, improved sperm density was observed (by 48.9% and 80.9%, resp.) and after 3-month treatment the sperm pathology decreased by 25.8%. Concentrations of CoQ(10-TOTAL) (ubiquinone + ubiquinol) and α-tocopherol were significantly increased and the oxidative stress was decreased. In conclusion, the effect of supplementary therapy with Carni-Q-Nol showed benefits on sperm function in men, resulting in 45% pregnancies of their women. We assume that assessment of oxidative stress, CoQ(10-TOTAL), and α-tocopherol in blood plasma and seminal fluid could be important metabolic biomarkers in both diagnosis and treatment of male infertility.