For patients with recurrent SCLC, topotecan remains the only approved second-line treatment, and the outcomes are poor. CheckMate 032 is a phase 1/2, multicenter, open-label study of nivolumab or nivolumab plus ipilimumab in SCLC or other advanced/metastatic solid tumors previously treated with one or more platinum-based chemotherapies. We report results of third- or later-line nivolumab monotherapy treatment in SCLC. In this analysis, patients with limited-stage or extensive-stage SCLC and disease progression after two or more chemotherapy regimens received nivolumab monotherapy, 3 mg/kg every 2 weeks, until disease progression or unacceptable toxicity. The primary end point was objective response rate. Secondary end points included duration of response, progression-free survival, overall survival, and safety. Between December 4, 2013, and November 30, 2016, 109 patients began receiving third- or later-line nivolumab monotherapy. At a median follow-up of 28.3 months (from first dose to database lock), the objective response rate was 11.9% (95% confidence interval: 6.5–19.5) with a median duration of response of 17.9 months (range 3.0–42.1). At 6 months, 17.2% of patients were progression-free. The 12-month and 18-month overall survival rates were 28.3% and 20.0%, respectively. Grade 3 to 4 treatment-related adverse events occurred in 11.9% of patients. Three patients (2.8%) discontinued because of treatment-related adverse events. Nivolumab monotherapy provided durable responses and was well tolerated as a third- or later-line treatment for recurrent SCLC. These results suggest that nivolumab monotherapy is an effective third- or later-line treatment for this patient population.