Blau syndrome (BS) is a rare granulomatous inflammatory disease presenting in early childhood as dermatitis, arthritis, and uveitis. Here, we describe a case of hydrocephalus in a patient with sporadic BS. A 36-year-old female, with mutations in the NOD2 gene on chromosome 16, who had been diagnosed with BS at the age of 19 years, had visual impairment and required support when walking for a long time. She was admitted to our hospital due to deterioration in her walking ability and an inability to stand by herself. We diagnosed an obstructive hydrocephalus based on head MRI. The aqueductal stenosis and obstructive hydrocephalus associated with granulomatous lesions were considered in this case. After third ventricle fenestration, her standing movement and walking improved immediately.