Chiari malformation type I (CM1) is an abnormality of the craniovertebral junction characterized by the caudal descent of the cerebellar tonsils through the foramen magnum. This malformation alters the cerebrospinal fluid (CSF) dynamics, leading to intracranial hypertension, brainstem compression, and several neurological symptoms, including headache. Headaches associated with CM1 have distinct characteristics, such as occipital localization and exacerbation by Valsalva maneuvers (coughing, sneezing, and physical exertion), and may experience significant relief following surgical decompression. This chapter explores the pathophysiology, clinical presentation, diagnostic strategies, and treatment of this disease using a fictional case report of a 42-year-old woman who had been experiencing a moderate, intermittent occipital headache and episodes of dizziness and postural instability for five years. Over the six months preceding her consultation, the frequency and intensity of the pain increased. The headache worsened with Valsalva maneuvers and partially improved with rest. She also reported intermittent paresthesia in the upper limbs and hand numbness upon waking. Magnetic resonance imaging (MRI) of the posterior fossa and cervical spine revealed cerebellar tonsils displaced seven millimeters below the foramen magnum and a syringomyelic cavity extending from C2 to C6. The cine MRI identified an increased CSF flow velocity, consistent with CM1. This case highlights the importance of considering CM1 in patients with occipital headache, pain exacerbated by Valsalva maneuvers, and sensory disturbances.