BACKGROUND: Myxomatous cerebral (oncotic) aneurysms following atrial myxoma is a rare neurological complication. CASE REPORT: We report an 11-year- old boy with left atrial myxoma and multiple cerebral oncotic aneurysms. The characteristics of these aneurysms are indefinite and variable. The "Metastasize and Infiltrate" theory may be the key mechanism in the formation of these aneurysms. CONCLUSIONS: Magnetic resonance imaging (MRI), computed tomography (CT) and angiography are useful in the diagnostics while digital subtraction angiography (DSA) is the best option. There are no definite guidelines for therapy of these aneurysms. Resection of cardiac myxomas, chemotherapy, radiotherapy, coil embolization and surgical treatment could be helpful.