Osteopetrosis is an uncommon congenital disorder characterized by defective osteoclastic resorption of bone that results in increased bone density. Clinical symptoms include anemia, hepatosplenomegaly, and cranial nerve and/or brainstem compression and hydrocephalus due to foraminal narrowing in the skull. The authors present an unusual case of a patient with autosomal recessive osteopetrosis associated with extensive calcification of the dura mater covering the brain as well as obstructive hydrocephalus. Ventriculoperitoneal shunt treatment was complicated by persistent overdrainage. It is suggested that chronic progressive triventricular hydrocephalus developed as a result of acquired aqueductal stenosis caused by extensive calcification of the tentorium cerebelli and calvarial hyperostosis. To the best of the authors' knowledge, this has not been described in the literature.