Sinus pericranii (SP) is a rare vascular anomaly of the scalp that consists of an abnormal pericranial venous channel connected to adjacent dural venous sinuses. Most SP are asymptomatic and are found in the pediatric age group. We aim to report a case of symptomatic SP in adult and describe the clinical, radiological, and pathohistological findings to help understand and differentiate this lesion from other scalp lesions. A 40-year-old man with a scalp mass was admitted to our hospital complaining of headache. The lesion enlarged when the patient was in a recumbent position or during Valsalva maneuver. The radiologic imaging suggested its diagnosis as an accessory type of SP with boneerosion. Surgical resection and cranioplasty were successfully performed, and the related headache also gradually subsided. At the 3-year follow-up, there was no recurrence on magnetic resonance imaging.