Aim Postoperative delirium (POD) is a very common and serious complication after total joint arthroplasty (TJA), which is closely associated with many adverse consequences and a poor prognosis. This study aimed to establish the potential risk factors for POD. Methods In total, 336 patients who underwent elective TJA under general anesthesia between 2018 and 2021 were included and deemed eligible for inclusion. POD was diagnosed based on the criteria by the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM V). The receiver operating characteristic curve was drawn to evaluate the predictive and cut‐off values of continuous variables for POD. Potential risk factors for POD were evaluated by binary univariate and multivariate analysis with the “Enter” method. Results According to the criteria by DSM V, 43 patients were categorized into the POD group, with an incidence of 12.8% (43 of 336). The receiver operating characteristic curve showed that albumin/fibrinogen ratio (AFR) was a good predictor for POD with an area under the curve of 0.754, cut‐off value of 9.65, sensitivity of 57.00% and specificity of 83.72% (P <0.001). A low preoperative AFR level (<9.65) was determined as the only independent risk factor for POD by the univariate and multivariate logistic regression analyses (OR: 2.45, 95% CI: 2.01–2.94, P = 0.008). Conclusions Our results indicate that a low AFR is an independent risk factor for POD in elderly subjects after TJA. Geriatr Gerontol Int 2022; 22: 412–417.