Objective: To investigate the hepatorenoprotective effects of Origanum vulgare L. against finasteride-induced oxidative injury in the liver and kidney of mice. Methods: Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI/MS) analysis was utilized to yield a fingerprint of Origanum vulgare polyphenolic constituents. Thirty BALB/c mice received 0.5 mL/day distilled water, finasteride (25 mg/kg/day for 10 d), and 100, 200, or 400 mg/kg/day finasteride + Origanum vulgare extract with 6 mice per group for five weeks. On day 36, liver and kidney function as well as pro-and antiinflammatory (IFN-γ, IL-12, IL-6, TNF-α, IL-1β, and IL-10) cytokines were measured. The total antioxidant status, nitric oxide (NO), and malondialdehyde levels as well as the activities of NO synthase and catalase were also evaluated. Histopathological study was conducted to assess the effect of Origanum vulgare extract on finasteride-induced renal and hepatic toxicities. Results: Twenty-five major polyphenolic compounds were identified in the Origanum vulgare extract by LC-ESI/MS. Origanum vulgare extract, especially at 200 and 400 mg/kg/day doses, significantly improved liver and kidney biochemical indices, decreased inflammatory cytokines, increased total antioxidant status and NO synthase and catalase activities, as well as decreased plasma NO and malondialdehyde levels in a dose-dependent manner as compared to the finasteride group. Histopathological results further confirmed the protective effect of Origanum vulgare extract. Conclusions: Origanum vulgare extract ameliorates finasteride-induced hepatic and renal biochemical and histopathological alterations, and restores antioxidant/oxidant balance.