BACKGROUND: This ambispective study was designed to assess the efficacy and safety of avelumab maintenance in a real-world population of patients with metastatic urothelial cancer (UC). METHODS: Patients with metastatic UC and measurable disease that had not progressed following first-line platinum-based chemotherapy were treated with maintenance avelumab (800 mg administered every 2 weeks). The primary endpoint was overall survival (OS). RESULTS: A total of 110 patients were enrolled. The majority of patients were male (81%), with a median age of 65 years (range, 36-84). The median OS was not reached, with a 1-year OS rate of 78.7%. The median PFS was 9.5 months (95% CI, 7.8-11.2 months). The ORR to first-line chemotherapy was 48.2%, and an additional 34.6% of patients responded to avelumab therapy (16 complete and 22 partial responses). Grade 3 adverse events during avelumab therapy were experienced by 11.8% of patients. CONCLUSIONS: These findings demonstrate similar efficacy and safety of avelumab in a real-world setting when compared to data from pivotal study. TRIAL REGISTRATION: KCRB registry number: RAVE-Bladder.