Background: Delirium is a severe organic disorder in the brain and a type of disorder in the cognitive state associated with reduced attention and cognition. This study aimed to investigate the prevalence of delirium in patients undergoing hip joint surgery. Methods: In cross sectional study, the patient's demographic profile form and a checklist of intervening factors designed which were used to measure the prevalence of delirium. The researcher checked the delirium status of the patients on the day before the surgery, 6, 12, 24, and 48 hours after the surgery, and at the time of discharge. Ethical criteria in the research included obtaining informed consent of patients, keeping patients confidential, notifying the delirium status patients to the attending physician for further actions, and not imposing costs on patients. The data were analyzed using Spss software version 16 and descriptive and analytical tests. Results: Result showed, the overall prevalence of delirium in patients was equal to 58 (46.4%), and 92 (73.6%) of patients without a spouse, 112 (89.6%) of patients with poor economic status, 63 (50.4%) of smoking patients, 14 (11.2%) with a history of drug use, 54 (43.2%) with a history of hospitalization in the ICU. Also, the mean (SD) age of the patients was 75.44 (8.43). Conclusions According to the findings, the prevalence of delirium in patients with hip joint surgery was high, that is why it is necessary to carry out preventive interventions to reduce delirium in these patients.