Aims: To investigate the predictive value of frailty on postoperative complications in elderly patients undergoing major abdominal surgery. Study design: This was a prospective cohort study. Methods: Frailty phenotype assessment instruments were applied to evaluate the frailty of patients, and a self-designed questionnaire was employed to collect disease related data, including general demographics, a physiological index POSSUM score and an operative severity index. Postoperative complications were recorded during clinical follow-up. Differences in complications between groups were analysed to determine whether frailty was an independent influencing factor for postoperative complications in elderly patients undergoing abdominal surgery and to determine the predictive value of frailty. Results: The incidence of frailty in elderly patients undergoing abdominal surgery was 23.74% (n=176). The incidence of postoperative complications in the frailty group was 50% (n=32), significantly higher than that in the non-frailty group (7.64%, n=144; p<0.0001). Frailty was an independent influencing factor for postoperative complications in elderly patients undergoing major abdominal surgery. The area under the curve of frailty in the prediction of postoperative complications in elderly patients with major abdominal surgery was 0.757, indicating that frailty had the same predictive value as POSSUM. Conclusion: Frailty is an effective predictor for the occurrence of postoperative complications in elderly patients undergoing major abdominal surgery. Relevance to clinical practice: Frailty is related to the occurrence of postoperative complications to assess the surgical risk of patients. Frailty assessment provides a new tool for nurses involved with the preoperative care and risk assessment of elderly patients with surgical risk. © 2018, Scientific Publishers of India. All rights reserved.