Arnold-Chiari malformations are a group of congenital hindbrain and spinal cord abnormalities characterized by herniation of the contents of the posterior cranial fossa caudally through the foramen magnum into the upper cervical spine. It is important to recognize Arnold-Chiari type I malformation in the differential diagnosis of adult vertigo cases. We present a 51-year-old patient with Arnold-Chiari type I malformation that was initially diagnosed as posterior semicircular canal benign paroxysmal positional vertigo.