<p>Cowden syndrome is a rare autosomal dominant disorder marked by multiple hamartomas and increased cancer risk, especially breast, thyroid, and endometrial malignancies; it is usually caused by an inherited change in the phosphatase and tensin homolog (PTEN) gene. However, its cardiovascular manifestations remain poorly characterized. We report a case of a 4-year-old boy presenting with ascending aortic aneurysm, who required a Bentall de Bono operation, and whose genetic testing identified a pathogenic PTEN mutation. His family history revealed additional features consistent with Cowden syndrome. This case underscores a potentially under-recognized vascular phenotype associated with PTEN mutations and highlights the need for cardiovascular screening in affected individuals. The presence of aneurysms may significantly impact morbidity and mortality, especially in pediatric patients. Our findings support incorporating vascular imaging into routine surveillance of Cowden syndrome, particularly in patients with suggestive features or family history, to enable early intervention and reduce life-threatening complications.</p>