Hepatic hydrothorax is defined as pleural effusion with liver cirrhosis but no primary cardiopulmonary disease. Hepatic hydrothorax is often resistant to various therapeutic interventions. The most likely cause is the transfer of ascites fluid from the abdomen to the pleural space via the diaphragm because of a negative intrathoracic pressure gradient. A 62-year-old man was diagnosed with hepatoma and cirrhosis. After a partial hepatectomy, he suffered with hepatic hydrothorax. He had snoring without obvious sleep apnea. The patient's hepatic hydrothorax markedly improved following nasal continuous positive airway pressure (nCPAP) treatment during sleep. The mechanism for the improvement may have been the intrathoracic positive pressure during sleep induced by the nCPAP treatment during sleep. nCPAP treatment may provide a new therapy for resistant hepatic hydrothorax.