Background: Nivolumab has been approved in China as second-line treatment for advanced non-small-cell lung cancer (NSCLC) via weight-based infusion, based on the CheckMate 078 study. We investigated the safety and efficacy of 240 mg flat-dose nivolumab in patients with advanced NSCLC, including those with hepatitis B virus (HBV) and epidermal growth factor receptor ( EGFR) mutation/ALK receptor tyrosine kinase ( ALK) translocation due to high prevalence in China. Methods: CheckMate 870 was a single-arm, open-label, phase IIIb trial in Asian (primarily Chinese) patients with previously treated advanced NSCLC. Patients received flat-dose nivolumab 240 mg every 2 weeks (Q2W) for up to 2 years. The primary endpoint was the incidence and severity of treatment-related select adverse events (TRsAEs) in non-HBV patients; secondary and exploratory endpoints included severity of high-grade TRsAEs in HBV-infected patients, and safety, efficacy and patient-reported outcomes (PROs) in the whole population. Results: Out of 404 patients enrolled, 400 received treatment. Median (standard deviation) age was 60.5 (8.68) years and the majority were male (78.5%). At a median follow-up of 37.6 months, no Grade 5 TRsAEs were reported, and the frequency of Grade 3–4 TRsAEs was low (0.0–5.9%) in non-HBV and HBV NSCLC patients. Median overall survival (OS) and progression-free survival (PFS) in all treated patients were 14.7 (12.3–18.1) and 3.6 (2.3–3.8) months, respectively. Median OS was 14.2 (12.3–18.1) and 22.3 (10.0–NA) months for non-HBV and HBV-infected patients, 19.3 (11.2–31.7) and 13.7 (11.5–18.1) months for EGFR-positive and wild-type subgroups, and 19.3 (12.9–23.5) and 13.3 (10.9–17.7) months for those with programmed death-ligand 1 (PD-L1) expression ⩾1% and <1%, respectively. No notable changes from baseline were observed in PROs throughout the study. Conclusion: Nivolumab 240 mg infusion Q2W was well tolerated, efficacious, and maintained health status and quality of life in Asian patients with previously treated advanced NSCLC regardless of HBV, EGFR, or PD-L1 status.