Ejaculation is controlled by both the sympathetic and parasympathetic system and consists of an emission and expulsion phase. Ejaculation latency time is regulated by the sympathetic system. Hypothetically, by reducing ejaculatory latency time, spontaneous ejaculation can occur. Extending the duration of ejaculation is a well-known side effect of antidepressants, especially selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors and noradrenergic reuptake inhibitors. Adrenergic drugs are sometimes used as treatment for delayed ejaculation. A spontaneous ejaculation due to the use of these drugs has rarely been reported. Although most reports of spontaneous ejaculations are related to the use of venlafaxine and reboxetine, this study is based on a case of the side effect of duloxetine.