This study aimed to summarize the occurrence of immune-related adverse events (irAEs) and further evaluate their association with clinical outcomes in patients with advanced renal cell carcinoma (RCC) and urothelial carcinoma (UC) treated with immune checkpoint inhibitors (ICIs).A comprehensive search of PubMed, Embase, and the Cochrane Library up to December 2023 was conducted to identify eligible studies. The details of irAEs and data regarding their correlation with clinical outcomes were extracted. R software was used for meta-analysis.A total of 27 studies involving 6148 patients with RCC or UC were included. The pooled overall incidence for any-grade and grade ≥ 3 irAEs was 44.2 % (95 % CI: 38.1 %-50.5 %) and 15.7 % (95 % CI: 11.4 %-21.1 %), respectively. Compared to those without any irAEs, patients with irAEs showed improved PFS (HR = 0.44, 95 % CI: 0.35-0.56, p < 0.01) and OS (HR = 0.47, 95 % CI: 0.42-0.51, p < 0.01), as well as higher ORR (OR = 3.59, 95 % CI: 3.01-4.29, p < 0.01) and DCR (OR = 4.23, 95 % CI: 3.06-5.84, p < 0.01). Subgroup analysis indicated that clinical outcome improvements were associated with the occurrence of irAEs, regardless of tumor type or ICI agent. Notably, patients with cutaneous irAEs, thyroid dysfunction, and grade ≤ 2 irAEs had a higher probability to achieve better survival benefits from ICI-based therapy, while pulmonary irAEs and grade ≥ 3 irAEs seemed to have a negative impact on OS. Additionally, systemic glucocorticoids administration did not affect survival outcomes.Our findings suggest that the occurrence of irAEs could be considered as a potential prognostic factor for predicting the efficacy of ICIs in patients with advanced RCC and UC.Copyright © 2024 Elsevier Ltd. All rights reserved.