Previous studies have shown that seizure can induce cognitive impairment. On the other hand, soy phytoestrogens, which are mainly found in soybean (Glycine max (L.) Merr.), have beneficial effects on the nervous system. However, little is known about their probable effects on seizure. The present study aimed to examine the probable effects of soy extract, containing the phytoestrogen genistein on seizure-induced cognitive and synaptic plasticity impairment in Ovariectomized (OVX) rats. Rats were ovariectomized, implanted with guide cannula and then divided into 5 groups (n=7-8 in each group): PBS, KA, Saline-KA, Higher Dose Soy (HDS-KA), and Lower Dose Soy (LDS-KA) groups. Animals of the HDS-KA and LDS-KA groups received intraperitoneal administration of soy extract (20 and 2 mg/kg, respectively) and the Saline-KA group received normal saline once a day for 4 days. Sixty minutes after the last injection, Kainic Acid (KA) or PBS was injected into the left lateral ventricle via pre-implanted guide cannula to induce generalized seizures. The Morris water maze task and in vivo field potential recordings were conducted 7 days later. Soy extract at both doses significantly improved learning impairment and at the higher dose (20 mg/kg) significantly prevented seizure-induced spatial memory impairment and deficit of long-term potentiation in the hippocampus. The soy extract containing the phytoestrogen genistein may have beneficial effects on memory deficit induced by seizure in OVX rats and this effect is accompanied by a beneficial effect on synaptic plasticity.