Background: In the phase 3 JAVELIN Bladder 100 trial (NCT02603432), avelumab 1L maintenance therapy + BSC showed significantly longer overall survival (OS) vs BSC alone in patients with advanced UC that had not progressed with 1L platinum-based chemotherapy. We report efficacy and safety results in patients enrolled in Asia. Methods: Patients with unresectable locally advanced or metastatic UC without disease progression after 4-6 cycles of gemcitabine + cisplatin or carboplatin were randomized 1:1 to receive avelumab 1L maintenance + BSC or BSC alone, stratified by best response to 1L chemotherapy and visceral vs nonvisceral disease when initiating 1L chemotherapy. The primary endpoint was OS, assessed from randomization in all patients and patients with PD-L1+ tumors (Ventana SP263 assay). Results: 147 Asian patients were enrolled at sites in Japan, South Korea, Taiwan, Hong Kong, and India; 73 and 74 were randomized to receive avelumab + BSC or BSC alone, respectively. Median OS (95% CI) was 25.3 mo (18.6 mo-not estimable [NE]) with avelumab+ BSC vs 18.7 mo (12.8 mo-NE) with BSC alone (HR, 0.74 [95% CI, 0.434-1.260]) in all patients, and 26.1 mo (18.2 mo-NE) vs 19.4 mo (11.9 mo-NE), respectively (HR, 0.66 [95% CI, 0.279-1.541]), in the PD-L1+ subgroup (n = 71). With avelumab + BSC vs BSC alone, median (95% CI) progression-free survival was 5.6 (2.0-7.5) vs 1.9 (1.9-1.9) months (HR, 0.58 [95% CI, 0.383-0.864]) in all patients and 6.8 (1.9-11.2) vs 1.9 (1.9-3.8) months (HR, 0.63 [95% CI, 0.336-1.172]) in the PD-L1+ subgroup; objective response rates (95% CI) were 9.6% (3.9%-18.8%) vs 2.7% (0.3%-9.4%) and 12.5% (4.2%-26.8%) vs 3.2% (0.1%-16.7%), respectively. The most common treatment-emergent adverse events (TEAEs) of any grade (any causality) in the avelumab + BSC arm were pyrexia (23.6%), constipation, nasopharyngitis, and rash (19.4% each); grade ≥3 TEAEs were anemia (9.7%), amylase increased (5.6%), and urinary tract infection (4.2%). Conclusions: Efficacy and safety data support the use of avelumab 1L maintenance as the standard of care in Asian patients with advanced UC that has not progressed with 1L platinum-based chemotherapy. Clinical trial information: NCT02603432.