Rarely, downbeat nystagmus can occur due to compression of the lower brainstem by the ectatic vertebral artery and be resolved by microvascular decompression. We present a case of a 67-year-old man with downbeat nystagmus associated with brainstem compression by ectatic vertebral artery. He presented with oscillopsia and vertigo. When he turned his head upward, his symptoms were aggravated and a gait disturbance occurred. Magnetic resonance imaging and computed tomographic angiography demonstrated compression of the medulla oblongata by the left ectatic vertebral artery and other medical causes of downbeat nystagmus were ruled out. Retromastoid craniotomy was performed and after lifting the vertebral artery off the medulla, a trough-shaped indentation in the lower brainstem was identified. The ectatic vertebral artery was repositioned and a Teflon was inserted between the brainstem and the ectatic vertebral artery. Postoperatively, downbeat nystagmus had disappeared.