Dual origin and fenestration of the vertebral artery (VA) are very rare anomalies. Understanding of these variations, however, is important because they can be misdiagnosed as a VA dissection. A 42-year-old woman presented with motor weakness and sensory disturbance of the right upper extremity. Radiologic evaluations showed ectatic change in the right VA and an arteriovenous fistula between the right VA and the vertebral vein. We decided on endovascular occlusion of the proximal right VA and its fistulous portion. During the endovascular procedure, we had misunderstood the dual origin and fenestration of the VA as a dissection. Thus, failure to recognize these anomalies might result in unnecessary anticoagulation or therapeutic intervention. Clinicians should be alert to such VA variations when making a diagnosis and when planning any intervention or surgery involving the proximal VA.