Soybean (Glycine max) from leguminosae family has many medicinal properties. Current study was carried out to evaluate the effects of soybean’s hydroalcoholic extract on sexual hormones in mice. Forty mice were randomly divided into five groups including control, placebo and three experimental groups. Cloprostenol was injected and three days later progesterone was injected to synchronize sexual cycles of samples. Hydroalcoholic extract was injected in 50 mg/kg, 100 mg/kg and 200 mg/kg doses intraperitoneal for twenty days every other day. At the end of period, blood samples were taken and LH, FSH, estradiol and progesterone hormones were measured using ELISA method. According to results, all doses of the extract reduced LH, FSH and estrogen hormones and increased progesterone significantly (p<0.05). Probably, soybean extract can affect sexual hormones and hypothalamuspituitary axis by phytoestrogens. Therefore, this plant can affect reproduction system of female mice.