Anomaly of basilar artery is rare, and basilar artery hypoplasia (BAH) is even rarer. A 37-year-old female who had bilateral tinnitus for two years visited hospital. Although physical examination, audiometry, electronystagmogram, electrocardiogram, and blood examinations were normal, magnetic resonance angiogram revealed BAH and right vertebral artery hypoplasia. An unknown association had been observed between BAH and bilateral tinnitus in our case. It is possible that arteriosclerosis gradually influenced her BAH and its arteriolar branches. Although the inner-ear cochlea or auditory nerve was spared, the auditory pathway in pons was injured. Therefore, antiplatelet and brain circulation promoter were conservatively recommended to reduce the vascular resistance of posterior circulation. Three months later, tinnitus subsided. Furthermore, it was uneventful in the following half a year.