Background: Modulatory and antioxidant effects of soy extract on the central nervous system have been reported. Aim: The effects of soy on learning and memory impairments induced by scopolamine and the brain tissues oxidative damage was investigated. Materials and Methods: The ovariectomized rats were divided: (1) Ovariectomized (OVX), (2) Ovariectomized – Scopolamine (OVX-Sco), (3) Ovariectomized -Scopolamine - Soy 20 (OVX-Sco-Soy 20) and (4) Ovariectomized -Scopolamine-Soy 60 (OVX-Sco-Soy 60). Soy extract was administered (20 or 60 mg/kg; i.p.) daily for 6 weeks before training in the passive avoidance (PA) test. Sco (2mg/kg) was injected 30 min after training in the PA test. Results: In PA test, the time latency to enter the dark compartment in OVX- Sco group was higher than OVX group (P<0.01). Pre-treatment by both doses of soy prolonged the latency to enter the dark compartment compared to OVX-Sco group (P<0.05- P<0.01). The brain tissues mallondialdehyde concentration as an index of lipid peroxidation was increased while, thiol content was decreased in OVX- Sco group compared to OVX group (P<0.05). Pre-treatment by soy lowered the concentration of MDA while, increased thiol concentration compared to OVX- Sco group (P<0.05- P<0.01). Conclusion: It was observed that soy prevented learning and memory impairments induced by scopolamine in OVX rats. The mechanism(s) might at least in part be due to protection against the brain tissues oxidative damage.