Background: We investigated the effects of carbamazepine (CBZ) on semen parameters in men with newly diagnosed epilepsy, by performing semen analysis before starting any antiepileptic drugs, and then after starting CBZ, to determine the role and effects of CBZ in creating abnormalities in sperm analysis in these patients.Methods: In this prospective study, eight male patients 20-40 years of age who were referred to the outpatient epilepsy clinic at Shiraz University of Medical Sciences, Iran, from 2009 to 2012, due to new-onset seizure(s) were studied. A semen analysis was performed. CBZ was started and after at least 3 months of taking CBZ, another semen analysis was requested to determine the changes in semen quality. Statistical analyses were performed using non-parametric Wilcoxon test.Results: Mean age of the patients was 28.5 ± 3.5 years. 7 (87.5%) patients had temporal lobe epilepsy and 1 (12.5%) had parietal lobe epilepsy. The mean follow-up period was 5.5 ± 0.9 months. We observed that semen quality (concentration, progressive motility, morphology) has significantly changed in patients with newly-diagnosed epilepsy after being treated with CBZ (P = 0.012 for all indices).Conclusion: This study shows the direct effects of CBZ in causing changes in semen quality in men with epilepsy. Abnormalities in sperm concentration, morphology and motility, which were observed in the current study, might play a significant role in causing reduced fertility in men with epilepsy.