The ductus arteriosus (DA) is a vascular shunt between the main pulmonary artery and the proximal descending aorta, allowing the oxygenated blood from the placenta to bypass the fetal pulmonary circulation and supply oxygen-rich blood to the systemic circulation. Anomalies within the ductus arteriosus can compromise fetal circulation. Ductus arteriosus aneurysm (DAA) is a localized saccular or tubular dilation of the DA and is considered a rare lesion. However, many reports in the literature describe DAA in the infancy period, with limited reports describing the lesion prenatally. We diagnosed a case of ductus arteriosus aneurysm with mild hypoplasia of the transverse arch prenatally at a 37-week gestational age. Both resolved spontaneously in the third week of life without complication.