Erectile dysfunction is a sexual dysfunction which is commonlycomorbid with major depression. Antidepressant treatment does notalways improve comorbid sexual dysfunctions in major depression. Infact, sexual dysfunction may worsen or get complicated following theintroduction of antidepressants. Modafinil is a drug with stimulanteffect on the central nervous system by binding to norepinephrineand dopamine transporters and consequently increasing synapticnorepinephrine and dopamine levels. Modafinil is primarily used inthe treatment of narcolepsy and chronic fatigue syndrome. In addition,it is known for its effectiveness in attention deficit hyperactivitydisorder and as an add-on option for major depression. In this paper,we report the case of a 39-year-old man with major depression whosecomorbid erectile dysfunction improved after addition of modafinilto antidepressant treatment. Fluoxetine 20 mg/day was initiatedand despite the improvement of most of the depressive symptomsand the sexual desire, his complaints of fatigue, weakness and erectiledysfunction continued. With the addition of modafinil (200 mg /day),improvement was observed not only in psychomotor symptoms but alsoin erectile dysfunction of the patient.