Aim: To investigate the effect of preoperative psychological intervention on postoperative pulmonary complications (PPCs), anxiety levels, hospital stay, and respiratory function in patients undergoing major elective abdominal surgery. Materials and Methods: This randomized controlled trial (RCT) included 120 patients, aged 18–70 years, classified as ASA I–III, who were scheduled for major elective abdominal surgery. Participants were randomized into two groups: an intervention group (n=60) receiving structured preoperative psychological intervention and a control group (n=60) receiving standard preoperative care. The psychological intervention consisted of three 45-minute sessions, covering psychoeducation, breathing and relaxation techniques, and cognitive-behavioral coping strategies. Primary outcomes were the incidence of PPCs (including pneumonia, atelectasis, and prolonged oxygen requirement), while secondary outcomes included anxiety levels, length of hospital stay, and respiratory function assessed via spirometry. Results: PPC incidence was significantly lower in the intervention group, with reductions in pneumonia (8.33% vs. 20%) and atelectasis (13.33% vs. 25%) (p=0.03 and p=0.04, respectively). Prolonged oxygen requirement was observed in 5% of the intervention group compared to 13.33% in the control group (p=0.02). Anxiety levels pre-surgery and post-surgery were significantly lower in the intervention group (p=0.01 to p=0.03). Hospital stay was shorter in the intervention group (6.4 ± 1.2 days vs. 8.1 ± 1.5 days, p=0.02). Respiratory function was consistently higher in the intervention group across postoperative days 1, 3, 5, and 7 (p=0.01 to p=0.04). Conclusion: Preoperative psychological intervention effectively reduces PPCs, lowers anxiety, shortens hospital stay, and improves respiratory function in patients undergoing major surgery. Integrating structured psychological preparation into preoperative care may enhance surgical outcomes and patient satisfaction.