BACKGROUND Patients undergoing cardiac surgery require postoperative chest drainage. However, the drain is difficult to keep in place in children with congenital heart disease. Since 2015, at Kyungpook National University Hospital, the chest tube is removed on postoperative day 1 in patients who have undergone simple congenital cardiac surgery (i.e., closure of an atrial or ventricular septal defect). In this study, we evaluated the relationship between the duration of drain placement and the likelihood of pericardial effusion after congenital cardiac surgery. METHODS The medical records of patients who underwent closure of an atrial or ventricular septal defect at our hospital between January 2014 and December 2016 were reviewed. In total, 162 patients who received follow-up echocardiography and had information available on postoperative pericardial effusion after the repair procedure were enrolled. RESULTS Echocardiography was performed at a median of 5 days (range, 4 to 6 days) postoperatively before discharge from the hospital. Pericardial effusion occurred in 21 patients (13.0%), of whom only 3 (1.9%) had moderate or greater pericardial effusion, regardless of the drain duration. All patients improved during outpatient follow-up without invasive management. No patient had severe complications because of pericardial effusion. The duration of drain placement did not affect the incidence of postoperative pericardial effusion (p=0.069). Operative survival was 100%. CONCLUSIONS Based on our study, we recommend removing the drain as soon as its role is complete, generally on postoperative day 1, because early removal does not increase the incidence of pericardial effusion in patients undergoing simple congenital cardiac surgery.