A 73-year-old male undergoing peritoneal dialysis (PD) for end-stage renal disease due to diabetic nephropathy was diagnosed with aortic stenosis and was admitted to our hospital in September, 2009. The patient underwent replacement of the ascending aorta with an artificial blood vessel plus aortic valve replacement without any notable complications. PD was restarted 3days after the surgery and large amounts of light red fluid from the drain placed in the pericardium were observed just after resumption of PD solution. The patient was diagnosed with peritoneopericardial communication. PD was discontinued and hemodialysis was performed only with intermittent lavage of the peritoneal cavity. The amount of drainage was spontaneously decreased, and on the 17th day after surgery, PD was resumed. The patient is undergoing PD without recurrence of peritoneopericardial communication, 59months after the onset of symptoms. Peritoneopericardial communication in a patient with PD developing after open-heart surgery is rare because such a case has been documented in only one case report. However, since massive pericardial effusion may cause severe cardiac problems, we consider that the communication between the peritoneal cavity and the pericardium needs to be checked for in patients with PD after cardiac surgery.