Therapeutic effect of Hypericum perforatum L. has been well known. The aim of this study is to investigate the anticonvulsant effects of Hypericum methanolic extract against seizure induced by picrotoxin in mice. The study were performed on four groups of animals. They received percolated extract of Hypericum perforatum at the doses of 25, 50, 100 & 200 mg/kg intra peritoneally. After 20 minutes animals received picrotoxin 10 mg/kg for induction of seizure. Latency of seizure, duration of seizure, death latency and percent of mortality were determined. The results indicated that latency of seizure increased in pretreated group with the dose of 50 mg/kg (p<0.01). The higher dose of extract 200 mg/kg significantly decrease duration of seizure and death latency. It maybe due to unknown ingredients in this plant or producing concentrations higher than the therapeutic level. The results showed that Hypericum perforatum L. at the dose of 50 mg/kg maybe have some beneficial effect in seizure induced by picrotoxin and this plant is suitable for continuing search in this field.