An 8-year-old girl who had undergone chronic hemodialysis for 1 year presented with respiratory distress 24 h after a hemodialysis session. She had a massive pleural effusion of the left chest that was shown to be hemothorax by thoracentesis. After chest tube insertion, drainage was maintained for 2 days. Pleural effusion recurred after withdrawal of the chest tube. The antecubital arteriovenous fistula on the left arm was found to have an excessive flow with a thrill which was felt all over her left shoulder and left hemithorax. The pleural effusion resolved spontaneously a week after ligation of the fistula. Excessive flow in the arteriovenous fistula was thought to be the cause of the hemothorax and should be included in the differential diagnosis of hemothorax in hemodialysis patients.