Portal vein aneurysm is a rare vascular disorder, particularly in the pediatric population, with relatively few cases reported in the literature. The most frequent complication of portal vein aneurysm is thrombosis, which may lead to diagnostic uncertainty as it can resemble a tumor. Therefore, it is important to recognize this entity and its imaging features for accurate diagnosis. We present a case of a portal vein aneurysm in an adolescent boy, complicated with thrombosis, and report radiological findings, treatment, and short-term follow-up.