Objective: This study aimed to measure preoperative stress in all patients undergoing cardiac surgery and to examine the relationship between preoperative stress and postoperative complications. Material and methods: The prospective study placed from Mar 2018-Dec 2019 at a single academic medical center. One hundred adults aged 18 to 65 who had undergone cardiac surgery consecutively were included in the analysis. The State Anxiety Inventory was used to quantify preoperative stress and assess its relationship to both postoperative pain and morphine usage. Result: The patient population is 67% men and 33% women, with an average age of 57 and 10 years. Before surgery, 66% of patients said they felt only a little bit of anxiety, while 34% said they were extremely anxious. Patients reporting moderate to severe anxiety (SA) before surgery had significantly higher mean pain ratings than patients reporting mild anxiety (MA). Patients who had moderate SA used much more morphine both during the procedure and thereafter than patients who did not experience stress. Conclusion: After cardiac surgery, patients that had moderate to severe stress before the procedure reported considerably greater levels of discomfort compared to that who had MA. Patients need greater analgesia postoperatively in addition to during surgery.