A rare case of an isolated iliac artery pseudoaneurysm was diagnosed in a neonate during the perinatal period. The pregnant mother had no family history of genetic disorders or connective tissue issues. Due to concerns about the risk of rupture, a caesarean section was performed at 37 weeks of gestation. Post-delivery imaging using contrast-enhanced computed tomography (CT) showed a mass in the left external iliac artery that compressed the external iliac vein. Further evaluation through computed tomography angiography (CTA) confirmed the presence of an aneurysm next to the iliac artery. The infant is currently asymptomatic and is being monitored through clinical follow-up. This case highlights the effectiveness of prenatal ultrasound in identifying isolated iliac aneurysms, underscoring its importance for clinical intervention and treatment.