Although the occurrence of cerebral aneurysms in pediatric age group describes as rare, giant ones are more commonly be found than in adults. Insufficient epidemiological information, their association with other medical comorbidities, diagnostic pitfalls, complex surgical anatomy, and issues should be considered during surgery to make them difficult to diagnose and manage. We report a 6-year-old boy with presenting complaint of acute-onset headache without any other symptoms and a small area of intracerebral hemorrhage detected on initial computed tomography (CT) scan. Primary evaluations failed to result in a definite diagnosis, and delayed vascular studies suggested vascular malformation or an aneurysm as the causative factor of hemorrhage. Surgical exploration led to the diagnosis of a giant partially thrombosed aneurysm at the A2 segment of the left anterior cerebral artery and successful clipping. One of our findings on preoperative CT angiography, "fountain sign," may be useful for the diagnosis of partially thrombosed aneurysms when active bleeding from the aneurysm has been ruled out. Fountain sign can be a useful finding in the diagnosis of partially thrombosed aneurysms. Vascular lesions should always be considered as the primary cause of intracranial hemorrhage in pediatrics despite negative initial studies. Therefore, close follow-up and using delayed and multimodality vascular evaluations are crucial for successful management.