Background: The purposes of this study were to determine whether adjuvant chemotherapy (AC) improved the prognosis of patients with high-risk upper urinary tract urothelial carcinoma (UTUC)and to identify the patients who benefited from AC. Methods: Among a multi-center database of 1014 patients who underwent RNU for UTUC, 344 patients with ≥ pT3 or the presence of lymphovascular invasion (LVI) were included. Cancer-specific survival (CSS) estimates were calculated by the Kaplan-Meier method, and groups were compared by the log-rank test. Each patient's probability of receiving AC depending on the covariates in each group was estimated by logistic regression models. Propensity score matching was used to adjust the confounding factors for selecting patients for AC, and log-rank tests were applied to these propensity score-matched cohorts. Cox proportional hazards regression modeling was used to identify the variables with significant interaction with AC. Variables included age, pT category, LVI, tumor grade, ECOG performance status and low sodium or hemoglobin score, which we reported to be a prognostic factor of UTUC. Results: Of the 344 patients, 241 (70%) had received RNU only and 103 (30%) had received RNU+AC. The median follow-up period was 32 (range 1-184) months. Overall, AC did not improve CSS (P = 0.12). After propensity score matching, the 5-year CSS was 69.0% in patients with RNU+AC versus 58.9% in patients with RNU alone (P = 0.030). Subgroup analyses of survival were performed to identify the patients who benefitted from AC. Subgroups of patients with low preoperative serum sodium (≤ 140 mEq/ml) or hemoglobin levels below the normal limit benefitted from AC (HR 0.34, 95% CI 0.15-0.61, P = 0.001). In the subgroup of patients with normal sodium and normal hemoglobin levels, 5-year CSS was 77.7% in patients with RNU+AC versus 80.2% in patients with RNU alone (P = 0.84). In contrast, in the subgroup of patients with low sodium or low hemoglobin levels, 5-year CSS was 71.0% in patients with RNU+AC versus 38.5% in patients with RNU alone (P < 0.001). Conclusions: High-risk UTUC patients, especially subgroups of patients with lower sodium and hemoglobin levels, could benefit from AC after RNU.