Tolvaptan is a new selective vasopression V2-receptor antagonist. We report our experience with a use of tolvaptan for preoperative fluid management in a patient with severe constrictive pericarditis. A 66-year-old man presented with heart failure symptoms derived from constrictive pericarditis. Chest X-ray showed right pleural effusion and chest computed tomography demonstrated severe pericardial calcification. Despite that he received optimal conventional medical treatments, his hemodynamic condition further exacerbated during hospitalization. We administered tolvaptan in an attempt to optimize preoperative fluid management. Tolvaptan was found to be remarkably effective in that regard. The body weight decreased and the heart failure symptoms improved. Pericardiectomy was performed successfully, and he recovered uneventfully.