We report a case showing supranuclear vertical gaze palsy and convergence nystagmus caused by a unilateral lesion of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). The patient was a 54-year-old female with mitral stenosis and regurgitation and atrial fibrillation, who suddenly developed vertigo and double vision. She was admitted to our hospital because of persisting diplopia 4 days after onset, although vertigo had resolved within 1 hour. On admission she was alert, but presented with supranuclear vertical gaze palsy and convergence nystagmus. Other cranial nerves were intact and motor strength, deep tendon reflexes, sensations were also normal. There were no cerebellar signs. Cranial MRI demonstrated a unilateral ischemic lesion at the left thalamo-mesencephalic junction that involved the unilateral riMLF. Cerebral angiography revealed no abnormalities. Vertical gaze palsy has been reported to be caused by a lesion involving bilateral riMLF or unilateral posterior commissure, and convergence nystagmus usually by a lesion near or within the dorsal mesencephalon. However, recent reports have demonstrated a histopathologic evidence that vertical gaze palsy was caused by unilateral riMLF lesion. The present case confirms clinically that both vertical gaze palsy and convergence nystagmus can be developed by a lesion of unilateral riMLF.