AimTo investigate the risk factors for postoperative delirium among elderly patients undergoing elective surgery for gastroenterological cancer.MethodsFrom May 2020 to March 2022, patients ≥75 years old with gastroenterological cancer who underwent radical surgery were enrolled. The geriatric assessment, including evaluations of frailty, physical function, nutrition status, and cognitive function, was conducted preoperatively. The confusion assessment method was used to diagnose postoperative delirium. A multivariate logistic regression analysis was used to determine risk factors for postoperative delirium.ResultsA total of 158 patients were eligible for inclusion in this study. Of these 53 patients (34%) developed postoperative delirium. In the univariate analysis, the age, regular use of sleeping drugs and benzodiazepine, Charlson Comorbidity Index score, performance status, Fried's frailty score, Vulnerable Elders Survey‐13 score, grip weakness, Short Physical Performance Battery (SPPB) score, Mini Nutritional Assessment Short‐Form score, and Mini‐Mental State Examination score were statistically associated with the incidence of postoperative delirium. In the multivariate analysis, a SPPB score ≤9, Mini Nutritional Assessment score ≤11, a Mini‐Mental State Examination score ≤24, and regular use of benzodiazepine were found to be independent preoperative risk factors for postoperative delirium.ConclusionCertain findings during the preoperative geriatric assessment, especially low SPPB, Mini Nutritional Assessment Short‐Form and Mini‐Mental State Examination scores, and regular use of benzodiazepine were risk factors for postoperative delirium in elderly patients undergoing gastroenterological surgery.