BACKGROUND: RC48 is an antibody-drug conjugate (ADC) specifically targeting HER2. Phase II and III clinical trials have proven its significant anti-tumor effect against locally advanced or metastatic urothelial carcinoma (la/mUC). This study aims to further assess the effectiveness and safety of RC48 for patients with la/mUC and provide insights for further clinical practice. METHODS: Retrospective analysis for 42 patients with la/mUC who underwent RC48 alone or in combination with PD-1 inhibitors therapy between 18 October 2022 and 1 May 2024 were conducted to assess effectiveness and safety of RC48. Descriptive statistics were used to summarize baseline characteristics, treatment-related adverse events, etc. Cox proportional risk model and the Kaplan-Meier method were applied to analyze patients' survival. RESULTS: We observed a median progression-free survival (mPFS) of 6.2 months, although median overall survival (mOS) has not been reached so far. An objective response rate (ORR) of 54.8% and a disease control rate (DCR) of 83.3% was also observed. Patients with first-line therapy, second- or later-line therapy and neoadjuvant therapy were observed disease remission with ORRs of 47.7%, 40.0% and 100.0%, respectively. The most common treatment-related adverse events (TRAEs) include hypoesthesia and elevated transaminases which affect over 90.0% of patients and mostly grade 1-2 in severity, and no treatment-related fatalities were found. CONCLUSIONS: This multicenter, real-world study confirms that RC48 alone or in combination with PD-1 inhibitors exerted a promising effectiveness and manageable safety for first-line, second- and post-line, and neoadjuvant therapy with la/mUC.