Intact atrial septum (IAS), occurring in ∼10% of patients with hypoplastic left heart syndrome (HLHS), conveys significant neonatal morbidity and mortality. Perinatal interventions have been described, but outcomes remain poor. We present a fetus with HLHS with IAS who underwent immediate novel postnatal atrial appendage anastomosis, thus achieving rapid left atrial decompression. (Level of Difficulty: Advanced.).