To evaluate the long-term safety and efficacy of atezolizumab monotherapy in Chinese patients with previously treated, locally advanced or metastatic non-small cell lung cancer (NSCLC).In this open-label, single-arm, multicenter study, patients received atezolizumab 1200 mg intravenously on Day 1 of each 21-day cycle. The primary endpoint was incidence of atezolizumab-related serious adverse events (SAEs). Secondary endpoints included other safety and efficacy measures. Patients with available tumor tissue and blood samples underwent biomarker analyses. Patients with available tumor biopsies underwent exome sequencing.The safety and evaluable populations included 101 and 97 patients, respectively. Exome sequencing data were available for 31 patients. Median follow-up time was 27.43 months. Atezolizumab-related SAEs and immune-related adverse events occurred in 25.7% and 47.5% of the safety population, respectively, and in the following subgroups: central nervous system metastases (n = 14), 35.7% and 35.7%; squamous NSCLC (n = 39), 33.3% and 53.8%. The 24-month overall survival rate was 37.4%. Median overall survival and progression-free survival by RECIST v1.1 were 15.31 and 2.86 months, respectively; objective response rate was 16.5% in the evaluable population. PRRC2C (odds ratio: 12.780, P = 0.014) and ZMYND8 (odds ratio: 19.963, P = 0.016) gene mutations were significantly enriched in atezolizumab responders vs non-responders. Patients with CD8+ TILs > 10% vs ≤ 10% were significantly more likely to be atezolizumab responders.No new safety concerns were raised, and clinically meaningful benefits of atezolizumab monotherapy were shown. The results of the biomarker analyses may guide future therapeutic strategies.Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.