Cardiac tamponade after heart surgery is of great concern. It increases perioperative mortality and morbidity. Late tamponade might be easily missed and difficult to be diagnosed clinically. It is thought that posterior pericardial window decreases the incidence of postoperative tamponade. Aim of the work : The aim of the study to evaluate the prophylactic role of posterior pericardial window( PPW) in preventing pericardial tamponade after heart valve surgery. Patients and Methods: Our prospective randomized comparative study included 640 patients collected by simple random sampling ,all patients were admitted in cardiothoracic surgery department-Zagazig University hospitals-Egypt, from January 2020 to May 2022 . They were divided into two groups group1ppw group and group 2 non ppw group and each group contains 320 patients. Results: There is statistical significant difference as regrading occurrence of late tamponade between both groups and also less developed new onset atrial fibrillation in PPW group. Conclusion : Pericardial window is easily to be performed technically