Aim: Anaplastic ependymoma is a highly aggressive tumor that can cause life threatening complications. The aim of the case presentation is to raise awareness of the existence of rare neoplasms with symptoms of increased intracranial pressure and brain herniation. Early suspicion, appropriate diagnosis and treatment can result in a complete cure. Case report: A four-month-old girl was referred to Clinical Hospital Center Rijeka by a primary care physician due to an increase in head circumference, irritability, and high-pitched cry. Physical examination revealed hypertonus, downward gaze (“setting-sun” sign), swollen veins over the scalp, bulging fontanelles and separated sutures. Brain ultrasound showed large hydrocephalus with left-sided supratentorial formation. Computed tomography demonstrated expansive formation of the left hemisphere with hypertensive hydrocephalus. Magnetic resonance imaging verified left supratentorial tumor measuring 100x62x74 mm (APxLLxCC). Dilated left lateral ventricle and the third ventricle were pushed to the right side, with subfalcine herniation of 11 mm. The patient was transferred the same day to the Clinical Hospital Center Zagreb for emergency neurosurgical intervention. Complete tumor resection was performed. Histopathological diagnosis was anaplastic ependymoma grade III. The postoperative course was uneventful. After recovery, the patient was transferred to our hospital for further treatment. Adjuvant chemotherapy according to the HIT 2000 protocol was carried out, without serious toxicity. Eight years after the end of the treatment, the girl is in continuous remission and regular physical growth and intellectual development. Conclusion: Anaplastic ependymoma is a rare pediatric tumor of uncertain prognosis. The mainstay of the treatment remains maximal safe surgery (ideally gross surgical resection), followed by adjuvant chemotherapy. Recent genetic studies have led to the identification of biologically distinct subtypes, suggesting more adequate means for risk stratification. Early diagnosis and appropriate treatment contribute to a successful outcome.