We report a case of constrictive pericarditis in which trace mitral valve regurgitation was detected preoperatively and temporarily worsened after a pericardiectomy was performed. The early postoperative data suggested that the increased mobility of the lateral wall, in conjunction with an increase in the left ventricular volume, might be one of the causes of the perioperative mitral valve dysfunction. The mitral valve function returned to the preoperative baseline thirteen months after the pericardiectomy.