This study aimed to evaluate the potential role of the Geriatric Nutritional Risk Index (GNRI) in predicting oncological outcomes and postoperative complications in UTUC patients undergoing radical nephroureterectomy (RNU) and to develop a nomogram incorporating GNRI to predict outcomes. A retrospective analysis was performed on 458 consecutive patients who underwent RNU in our center. According to nutritional scores, patients were divided into the following groups: low GNRI (GNRI ≤ 98) and high GNRI (GNRI > 98). Univariable and multivariable logistic regression were performed to investigate the role of GNRI in predicting the perioperative complications. The survival was compared with Kaplan - Meier curve, and test by log-rank tests. Risk factors associated with cancer-specific survival (CSS) and overall survival (OS) were evaluated using Cox proportional hazards regression model and were integrated into a nomogram for individualized risk prediction. The calibration and discrimination ability of the model were evaluated by concordance index (C-index) and risk group stratification. When compared with high GNRI, low GNRI had significantly lower survival (CSS, p < 0.001; OS, p < 0.001). Across all patients, multivariable analyses revealed that low GNRI was an independent prognostic factor (CSS, p = 0.007; OS, p = 0.005). Nomograms for 1-, 3-, and 5years of CSS and OS had good performance. Patients can be stratified into different groups based on the nomogram, with significant differences in OS and CSS. Further, GNRI was also found to be an independent risk factor for postoperative complications. The complication - prediction nomogram based on GNRI was also internally validated and showed good performance. The GNRI score is an independent predictor for the prognosis and postoperative complications of UTUC following RNU. This study presented a nomogram incorporating preoperative GNRI that might be used as a convenient tool to facilitate the preoperative individualized prediction of short- and long-term outcomes for patients with UTUC.