Patients with metastatic, platinum-resistant urothelial carcinoma (PRUC) have no Food and Drug Administration-approved therapies. The response rates to second-line chemotherapy have generally been < 20%, with a median overall survival of < 1 year. We report our experience with 6 heavily pretreated patients with advanced PRUC (ClinicalTrials.gov identifier NCT01631552) with the novel antibody-drug conjugate, sacituzumab govitecan (IMMU-132). This antibody-drug conjugate comprises the active metabolite of irinotecan, SN-38, conjugated to an anti-Trop-2 antibody. Trop-2 is widely expressed in ≤ 83% of urothelial carcinomas. Of the 6 patients, 3 had a clinically significant response (progression-free survival, 6.7 to 8.2 months; overall survival, 7.5+ to 11.4+ months). Sacituzumab govitecan was well tolerated. Because of these results, a phase II trial has been initiated. The present report highlights the promise of antibody-drug conjugates, such as sacituzumab govitecan, as a novel therapeutic strategy for the treatment of PRUC.