Selective serotonin reuptake inhibitors and serotonin norepinephrine reuptake inhibitors are the mainstay treatment for major depressive disorder, but whether their therapeutic mechanisms involve the dopaminergic system remains inconclusive. Eight participants with major depressive disorder were administered single-photon emission computed tomography with [99mTc] TRODAT-1 both before and after 24 weeks of antidepressant treatment to evaluate the change in striatal dopamine transporter (DAT) availability. All participants were responders (≥50% reduction in Hamilton Depression Rating Scale score). The DAT availability did not change (P=0.58), as the Hamilton Depression Rating Scale score decreased (P=0.02). Striatal DAT availability remains intact during long-term antidepressant treatment in patients with major depressive disorder.