Abstract: Background and purpose: As an immune checkpoint inhibitor, nivolumab has a high affinity for programmed cell death protein 1 (PD-1) on the surface of T cells and can restore the anti-tumor immune response of T cells by binding to it. This study aimed to retrospectively analyze the efficacy and safety of nivolumab in patients with stage Ⅲ B or Ⅳ non-small cell lung cancer (NSCLC) who had disease progression or intolerable toxicity during or after one prior platinum-containing regimen. Methods: Data of 30 NSCLC patients treated with nivolumab 3 mg per kilogram every 2 weeks between Jan. 2016 and Apr. 2019 in Shanghai Chest Hospital were collected. Patients were treated until disease progression or discontinuation due to toxicity or other reasons. All adverse events were collected and analyzed. Results: All adverse events were graded with the Common Terminology Criteria for Adverse Events (CTCAE 4.0). There were 25 patients who reported at least 1 adverse event. The common treatment-related adverse events with nivolumab were fatigue, erythema and anemia, and the most frequently reported was fatigue (50%). Three patients had treatment-related grade 3 adverse events (fatigue, anemia and total bilirubin increase), and no grade 4-5 event was reported. There was no discontinuation or death which was attributed to nivolumab. All treatment-related adverse events were mild (grade 1-2) without special treatment. A few patients showed hyperthyroidism and interstitial pneumonia, which improved after symptomatic treatment. Conclusion: Nivolumab shows better tolerance and manageable safety profile in previously treated patients with advanced NSCLC.