Chylothorax, a postoperative complication of CHD surgery, involves chyle accumulation in the pleural cavity, posing challenges in diagnosis and management. This retrospective study investigates the prevalence, aetiology, management, and outcomes of postoperative chylothorax in paediatric patients undergoing cardiac corrective surgery at a tertiary care centre over 15 years. Medical records of paediatric patients who underwent cardiothoracic surgery at the Children’s Heart Center at the American University of Beirut Medical Center between 2007 and 2022 were retrospectively reviewed. Data collection included demographic characteristics, blood parameters, chylous fluid characteristics, diagnostic criteria, treatment modalities, and hospitalisation details. Ethical approval was obtained, and descriptive statistics were employed using SAS 9.4. Among 2,997 children who underwent cardiothoracic surgery, nineteen cases of postoperative chylothorax were identified. The majority were females (63.2%) with a median age of 9 months. Glenn, Fontan, and Blalock–Taussig shunt-related surgeries were the most common operations associated with chylothorax. Single ventricle physiology was the predominant CHD observed (58%). Diagnosis relied primarily on clinical presentation, imaging studies, and triglyceride levels in pleural fluid. Treatment options included conservative dietary modifications, medical therapy such as octreotide, and surgical intervention if necessary. No mortalities were reported, and patients were adequately followed up. This study sheds light on postoperative chylothorax in paediatric cardiac patients, offering insights into its epidemiology, aetiology, clinical features, and treatment outcomes. While conservative and medical approaches effectively managed chylothorax in this group, larger studies are needed to develop standardised diagnostic and treatment protocols, improving outcomes in paediatric patients with postoperative chylothorax.