Introduction: Arterial catheters are widely used in intensive care units for continuous blood pressure monitoring and blood sampling. The patency of these lines is maintained by continuous flushing, usually with the addition of the anticoagulant heparin to the flushing solution. Normal saline solution can maintain patency of arterial and central venous pressure monitoring catheters. Aim of the Study: The aim of this study was to evaluate the effect between normal saline and heparin solution in arterial line flushing on platelet count. Methods: This was a prospective cross- sectional study conducted in the Department of Cardiac surgery of National Institute of Cardiovascular Disease (NICVD), Sher-E-Bangla Nagar, Dhaka, Bangladesh during the period from July 2016 to June 2017. This study included sixty patients who underwent single valve replacement surgery and shifted to the ICU with arterial line catheter. The patients who fulfilled the inclusion criteria were divided into two groups- Group A (with heparin solution) and Group B (with normal saline). Result: In total 60 patients from both the groups completed the study. In our study we found the mean ± SD of age among group A & B was (36.3±6.7) & (35.7±10.3) respectively. We found the mean± SD of platelet count at 1st POD was (206530±64441) & (212543±48768); at 3rd POD was (226517±60185) & (245957±52826); at 7th POD was (240517±57379) & (257713±53655); at 14th POD was (245850±52680) & (244337±56796) in Group A & B respectively. Conclusion: In our study we didn’t find any statistically significant difference regarding the patients’ demographic characteristics and there were no statistically significant difference of platelet counts between Group A and Group B at preoperative period, post pump, 1st POD, 2nd POD, 3rd POD, 4th POD, 7th POD and 14th POD.