Abstract: The present experimental study was designed to investigate to elucidative effect of forced swimming stress on female mice fertility with emphasis on oocyte number and their quality and ultimately their in vitro fertilization capacity. A total 30 adult NMRI (Noda Medical Research Institute) mice randomly divided into two equal groups (n = 15); 1) control and 2) experimental groups. The control group remained in their cages, but experimental group was submitted to forced swimming for 3 min in water at 32°C daily for 50 days. The NMRI female mice in two group of study who mention above were administered intra-peritoneally with 5 IU pregnant mare serum gonadotropin (PMG) for superovulation. This was followed 46-48 h later by the intraperitoneal administration of 5 IU Human Chorionic Gonadotropin (hCG). Mice were euthanized 12-14 h after HCG injection by cervical dislocation method and oocytes collected from fallopian tube. Then count and quality of oocyte were assessed. In order to evaluated of fertilization capacity, a pre-incubated capacitated sperm was gently added to the freshly collected ova of two groups of study and two-cell embryos was counted 24-26 h after completion of fertilization in vitro. The fertilization capacity of oocyte of exposed to forced swimming stress was significantly lower than control groups (p<0.05). The plasma level of FSH and LH was significantly increased in stress mice group (p<0.05). The data of this present study clearly showed that forced swimming stress do not alter number of oocyte extraction but quality of extracted oocyte significantly decrease in mice exposed to forced swimming stress.