BACKGROUND Hydrocephalus and cerebellar abscesses as the principal manifestations of posterior fossa dermoid cyst are rare. In addition, extradural dermoid cyst of the posterior fossa has been described in only 9 cases in the literature. We present an unusual case of obstructive hydrocephalus due to cerebellar abscesses induced by an adjacent extradural dermoid cyst with complete occipital dermal sinus. METHODS A 14-month-old child presented with acute raised intracranially pressure, seizures, and meningitis. Neuroradiological studies revealed cerebellar cysts with ring enhancement associated with a contiguous occipital cyst, with compression of the adjacent cisterns and the fourth ventricle causing hydrocephalus. The diagnosis of cerebellar abscesses with congenital occipital defect was briefly entertained. The patient was treated by radical excision of the occipital cyst with hair contents, the dermal sinus, and the abscesses through a suboccipital approach, followed by systemic antibiotic therapy with a good outcome. Pathologic examination revealed a dermoid cyst. CONCLUSIONS Posterior fossa dermoid cyst should be considered in all children with occipital skin lesions, especially dermal sinus. CT scan and MRI are the methods of choice for further investigation of suspect congenital dermal lesions. Neurosurgical treatment of these malformations should be planned early to prevent the high incidence of infections such as bacterial meningitis and cerebellar abscess. Clinical presentation, diagnostic evaluation, and treatment of these rare lesions are reviewed.