Postoperative pulmonary complications are common and lead to increased morbidity and mortality in patients. These complications are observed especially after major surgical interventions. Breathing exercises performed with or without the use of a device are extremely important in preventing postoperative pulmonary complications. Breathing exercises that increase total lung capacity by encouraging the use of the diaphragm reverse alveolar collapse and postoperative hypoxemia. This study aim to determine the effect of postoperative respiratory exercise diary use in patients undergoing major abdominal surgery on dyspnea, fatigue, respiratory parameters (respiratory rate, SPO2, cough, sputum), early pulmonary complications, spirometry use and functional capacity.The research is planned to be conducted in a single-blind, randomized controlled manner. In the study, 60 patients (30 intervention and 30 control) who underwent major abdominal surgery will be included.Data will be collected using the Patient Introduction Form, Visual Analogue Scale, Medical Research Board Scale, 2-minute walk test, breathing exercise diary and patient follow-up chart.Patients in the intervention and control groups will be visited by the researcher for 3 postoperative days, respiratory parameters, cough, and sputum status will be recorded in the patient follow-up chart, and the use of a respiratory exercise diary will be evaluated.