Objective To investigate the prevalence of postoperative delirium (POD) in elderly patients undergoing major orthopedic surgery and analyze its influencing factors, so as to provide evidence for early screening and intervention of POD. Methods The medical records of elderly patients undergoing major orthopedic surgery in the Department of Orthopaedics of the First Medical Center, Chinese PLA General Hospital between January 2021 and December 2022 were retrospectively collected. The included patients were divided into POD group and non-POD group. The patients’ demographic characteristics, medical history, laboratory indicators, perioperative medication, intraoperative and postoperative indicators were collected to analyze the risk factors affecting POD. Results A total of 455 elderly patients were included. Among them, there were 75 cases in the POD group and 380 cases in the non-POD group. The incidence of POD was 16.5% (75/455). There were statistically significant differences in age, body mass index, number of combined underlying diseases≥3, albumin<35 g/L, American Society of Anesthesiologists (ASA) classification, intraoperative blood loss≥200 mL, intraoperative blood transfusion, postoperative Visual Analogue Scale (VAS) score, indwelling catheters, admission to intensive care unit (ICU), and length of ICU stay between the two groups (P<0.05). The results of logistic regression analysis showed that age≥79 years, number of combined underlying diseases≥3, albumin<35 g/L, intraoperative blood loss≥200 mL, ASA grade≥Ⅲ, postoperative VAS score, and postoperative admission to ICU (P<0.05) were independent influencing factors for POD occurrence in elderly patients undergoing major orthopedic surgery. Conclusions POD is one of the common postoperative complications in elderly patients undergoing major orthopedic surgery. Age≥79 years, number of combined underlying diseases≥3, albumin<35 g/L, intraoperative blood loss≥200 mL, ASA grade≥Ⅲ, postoperative VAS score, and postoperative admission to ICU are independent risk factors for POD in elderly patients undergoing major orthopedic surgery. Clinical staff should evaluate and screen these factors early and take preventive measures to reduce the incidence of POD.