Aims: This study aimed to determine the effect of 50 days of forced swimming stress on fertilization capacity of rat and subsequent offspring quality. Setting and Design: The prospective study designed in vivo. Materials and Methods: Total 90 Wistar rats including 30 adult male (3 months of age, weighing 210 ± 10.6 g) and 60 female rats (3 months of age, weighing 230 ± 12.2 g) were engaged in this study. Male rats were randomly divided in two equal groups (n=15): Control and experimental groups. Animals of the experimental group were submitted to forced swimming stress for 3 min in water at 32oC daily for 50 days. Then all adult male rats were mated with normal females (2 per each male) for 7 days. Female rats were sacrificed and autopsy was performed on day 20 of pregnancy when uterus and ovaries were examined for the number of corpora lutea, dead and live fetuses, embryo resorption, implantation sites, and fetus weight. Conclusion: Results of this study have important implications for families attempting pregnancy. Stress pursuant to life events may have a negative impact on in vivo fertilization capacity of male rats and subsequent offspring quality.