The anomalous origin of a hypoplastic Left Vertebral Artery (LVA) from the aortic arch is a rare anatomic variant. This study discusses the case of a patient with a C1 lateral mass tumor that surrounded a dominant Right Vertebral Artery (RVA) according to preoperative computed tomography angiography, with a hypoplastic LVA originating from the aortic arch. Surgery was performed, and the patient recovered uneventfully. To date, no study has reported the simultaneous association of two variations (origin and diameter) in the LVA. A deep understanding of abnormalities in the diameter and origin of LVA is a must for neurosurgeons as well as for thoracic and vascular surgeons to conduct surgical procedures.