Objective: This study sought to evaluate the protective effect of ethanolic leaf extract of Moringa oleifera on testosterone-induced benign prostatic hyperplasia (BPH) in male Sprague-Dawley rats. Materials and Methods: BPH was induced in rats by the administration of testosterone propionate (3 mg/kg, s.c., in olive oil) for 4 weeks. M. oleifera (50, 100, or 200 mg/kg), celecoxib (20 mg/kg), or M. oleifera (50 mg/kg) + celecoxib (20 mg/kg) were orally administered daily 15 min before testosterone. On day 29, blood was collected to measure the levels of serum testosterone and prostate-specific antigen before the animals were sacrificed. The prostates were weighed, assayed, and histologically examined. Results: M. oleifera significantly reduced the testosterone-induced increase in prostate weight (20.16%), prostate index (65.85%), serum testosterone (72.86%), and prostate-specific antigen (48.49%). Testosterone caused a significant increase in malondialdehyde (73%) as well as a reduction in glutathione (62.5%), superoxide dismutase (50%), and catalase (64%) activities which were attenuated by M. oleifera with a peak effect obtained at 100 mg/kg. The disruption of prostate histoarchitecture by testosterone was also ameliorated by M. oleifera. Conclusion: M. oleifera prevented testosterone-induced BPH through enhancement of antioxidant defence mechanisms, and hence could be used as an adjunct in the treatment of BPH.