Abstract Background and aim: Zonisamide is an inhibitor for glutamate neurotransmitter and gamma aminobutiric acid (GABA)-mediators. It also increases the total levels of serotonin. According to the importance of this drug in psychotherapy, its side effects on the endocrine system seem to be very important. This study was aimed to determine the effects of zonisamide on pituitary-gonad axis and spermatogenesis. Methods: In this experimental study, 50 adult male Wistar rats were divided in five groups of ten. The control group did not receive any medical treatment. The sham group received 1 ml distilled water as a solvent and three experimental groups were treated with 50, 100, 200 mg/ kg of zonisamide orally for 28 days.At the day of 29, blood samples and preparation of tissue section were taken from all groups. Serum concentrations of hormones were measured via Radio Immuno Assay (RIA). Using the SPSS software, the results were analyzed by using one-way analysis of variance (ANOVA) and Tukey tests. Results: The results showed that 100 and 200(mg/kg.b.w) of zonisamide could reduce the serum level of testosterone and dihydrotestosterone (DHT), while it increased the LH concentration. It should be noted that 200(mg/kg.b.w) of drug also enhanced the FSH level (P<0/001). Also, a considerable decline was observed in spermatogenesis chain at high doses of zonisamide. Conclusion: This study showed that high doses of zonisamide decrease the serum concentration of testosterone and dihydrotestosterone and the number of spermatogenic cells. It also increased the serum FSH and LH levels. Therefore, it is proposed that zonisamide may decrease the function of reproductive activity. Key words: Zonisamide, Reproduction, Rat