Background/objective: Acne vulgaris is one of the most common diseases of the youth. Systemic isotretinoin is the only drug which acts on all of the etiopathogenic mechanisms of acne. Isotretinoin has some well-known side effects. Besides these, there is a suspicion whether it causes infertility or not. In this study, we aimed to evaluate the effects of systemic isotretinoin on male fertility.Methods: Eighty one male patients, who were older than 18 years of age, and had severe or refractory acne vulgaris were included in the study. They were given a total dose of 120 mg/kg of systemic isotretinoin over a period of six months. Before and after the study, the spermiogram parameters of the patients were evaluated to show any possible effect on male fertility. The patients' total testosterone, follicle stimulating hormone and luteinizing hormone levels were also evaluated.Results: All of the spermiogram parameters changed positively (p<0.05). There was no significant change in the hormone levels.Conclusion: Systemic isotretinoin has a positive effect on male fertility. Since the hormone levels did not change significantly, this positive effect of isotretinoin is not via the hypothalamic-pituitary-gonadal axis but can be due to its regenerative and proliferative effects on the testes.