The introduction of adjuvant immunotherapy with immune checkpoint inhibitors (ICIs) has significantly changed the management of high-risk urological cancers, particularly clear cell renal cell carcinoma and muscle-invasive urothelial carcinoma. This review provides a comprehensive narrative overview of immune-related adverse events (irAEs) associated with adjuvant ICIs, integrating evidence from pivotal registrational trials and real-world clinical experience. Clinical studies and reports were reviewed to characterize the incidence, type, severity, and management of irAEs. Across registrational trials, endocrine, cutaneous, and gastrointestinal toxicities were the most frequently reported irAEs and were predominantly mild to moderate in severity. Severe events were less common and required early recognition and structured management, often including corticosteroids and targeted immunomodulatory therapies. In our real-world cohort, irAEs occurred in 5 of 13 patients (38.5%) receiving adjuvant anti-PD-1 therapy, mainly involving endocrine and cutaneous systems, with a frequency and severity profile consistent with that reported in the KEYNOTE-564 and CheckMate-274 trials. Most irAEs were grades 1–2 according to CTCAE criteria and were manageable with standard treatments; permanent discontinuation of immunotherapy was required in a single case. Overall, the integration of clinical trial data and real-world evidence supports a favourable and manageable safety profile of adjuvant ICIs in high-risk urological cancers. Multidisciplinary management remains essential to optimise patient outcomes.