Introduction: Pericardial effusion and tamponade are accounted as the two most important complications following open-heart surgeries which are known to increase mortality and morbidity rates. Putting a low negative pressure suction on the chest tube of patients might be a useful way for better drainage and also reducing the occurrence of pericardial effusion and tamponade. In the present study, we aimed to compare the prevalence of pericardial effusion and tamponade in patients undergoing open-heart surgeries with and without low negative pressure suction on the chest tube. Methods: This clinical trial was performed in 2018-2019 in Tehran, Iran. 100 patients who were candidates for open-heart surgery were entered. After surgeries, patients were divided into two groups: group 1 had a low negative pressure suction on their chest tube and group 2 had no suction. Patients were then observed for clinical and imaging characteristics of pleural effusion and tamponade. Data were gathered and analyzed using SPSS software. Results: In the present study, we indicated that the prevalence of pericardial effusion is significantly lower in patients with low negative pressure on their chest tube (P=0.04). No significant differences were observed between two groups regarding to: frequency of tamponade and post-operative ejection fraction (P> 0.05). Conclusion: The usage of a low negative pressure suction on the chest tube following open cardiac surgeries is associated with a lower prevalence of pericardial effusion. We suggest that such systems could be commonly used in cardiac surgeries or surgeries of the thorax.