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Priapism is an abnormal prolonged, painful erection without sexual stimulation. Antipsychotics, valproate, trazodone, methylphenidate, citalopram-induced priapism have been reported in the literature. Mirtazapine-induced-priapism has not been reported yet. We aimed to report a case of mirtazapine-induced-priapism He is a 47-year-old-married male, who applied to a psychiatrist with abuse of alcohol and the contamination obsessions, washing hands excessively. His medications at the time of admission were mirtazapine 30 mg/day and diazepam 10 mg/day. On the first day of treatment he had painful erection. Department of Urology confirmed priapism and planned an emergency treatment. He had a 37-year history of alcohol-cigarette use. He had his last alcohol use three weeks ago and cigarette fifteen months ago. He had no use of illicit-drug or another medication, disease like sickle-cell-anemia, perineal-trauma, that are known to cause priapism. His medications were stopped and penile corporal aspiration was made. He was medicated with diazepam 5mg/day as recommended by an urologist, post-operatively. And no priapism has been seen later. Mirtazapine is a commonly used presynaptic-alpha-2-antagonist that has dual-action by increasing noradrenergic-serotonergic neurotransmission. It has only a weak affinity for 5-HT1-receptors and has very weak muscarinic-anticholinergic and histamine antagonist properties. In contrast to SSRIs, mirtazapine has no sexual-side-effects. However, we thought that in this case priapism was associated with mirtazapine. No other risk factors was detected for priapism. Priapism occurred after initiation of mirtazapine and diazepam. Diazepam was continued for two weeks after operation and priapism was not seen again. Patient had a history of regular alcohol use but in the last three weeks, he did not use any alcoholic beverage. According to our investigation there is only one case of priapism induced by the combination of mirtazapine and trazodone. Erection control is provided by neurotransmitters affecting smooth muscle tone, hormones, vasoactive substances, signal transmission systems, corporeal tissue, cellular and molecular factors (i.e. nitric-oxide (NO) activity). Alpha-2 antagonists increase NO level and thus contribute to the relaxation of the smooth-muscles, arterioles of corpus cavernosum. Alpha-1-adrenergic-blockade decreases local adrenergic activity and venous-drainage is interrupted. The most important mechanism that causes unevenness on penile-vascular structures is Alpha-1 adrenergic-receptor-blockade and it is also the reason of priapism depending on psychotropics. Mirtazapine may be causing priapism by its alpha-2-adrenergic-receptor antagonist and muscarinic anticholinergic effects. In conclusion, priapism, a relatively uncommon disorder, is a medical emergency. Although mirtazapine is known to have low sexual side effects, priapism due to mirtazapine may rarely be seen.