Abstract: Medicinal plants are considered as natural sources of antioxidant compounds which may protect organisms against oxidative stresses. The present study was conducted to investigate the antioxidant potential of lemon verbena (Lippia citriodora). This clinical investigation was performed on a group of 43 healthy subjects. They were invited to use 3 mg of lemon verbena leaves as infusion daily at the morning and evening for two weeks. At the beginning and the end of investigation, blood samples were taken to study their lipid peroxidation levels and antioxidant activities beside the total thiol groups. At the end of experiment, data were subjected to the paired t-test analysis. After treatment, the total antioxidants of serum (1.95±1.1 vs. 1.67±0.95 μmol mL-1) significantly increased while the lipid peroxidation reduced (12.23±9.35 vs. 15.66±12.15 nmol mL-1). The treatment had no significant effect on the total thiol groups. Lemon verbena is beneficial in improving body oxidant/antioxidant balance and thus its clinical efficacy remains to be tested in oxidative-stress-related diseases or conditions. Use of this herbal extract is recommended as a dietary supplement.