We report a case of right chylothorax associated with physical abuse in a 10-month-old boy who presented with respiratory decompensation. Chylothorax was improved by thoracic drainage and nutrition management, such as fasting followed by medium-chain triglyceride milk. Chest computed tomography on admission showed bilateral old rib fractures. Accordingly, physical abuse was suspected. Chylothorax of unknown cause in infancy, especially in those with coexisting rib fractures, must be scrutinized for child abuse.