Background: Immunochemotherapy has become a standard first-line regimen for advanced non-small-cell lung cancer (NSCLC). Several studies showed the synergistic effects of immunotherapy and radiotherapy on local and abscopal tumour control. But the data of first-line immunochemotherapy combined with radiotherapy for the advanced NSCLC is still scarce. Methods: Patients with advanced NSCLC receiving first-line PD-1 inhibitors immunotherapy plus chemotherapy in a single center were retrospectively analyzed in this study. They were divided into two groups according to whether they had received radiotherapy. The efficacy and safety of first-line immunochemotherapy combined with radiotherapy (ICRT group) and immunochemotherapy alone (ICT group) were investigated. Results: A total of 135 patients were included; 65 patients received PD-1 inhibitors plus chemotherapy and radiotherapy, while other 70 patients were treated with immunochemotherapy alone. The median interval time between radiotherapy and PD-1 inhibitors immunotherapy was 5 days (range, 0-96 days). The overall response rate (ORR) was 50.8% in the ICRT group and 40.0% in the ICT group, respectively. Patients in the ICRT group achieved significant longer progression-free survival (PFS, median 16.5 vs 10.4 months, P= 0.043) and overall survival (OS, median not reached vs 21.0 months, P= 0.030) compared with those in the ICT group. The addition of radiotherapy was the only prognostic factor for PFS (HR = 0.617, 95%CI: 0.385-0.989, P= 0.045) and OS (HR = 0.512, 95%CI: 0.277-0.947, P= 0.033) by univariate Cox regression analysis. Patients were well tolerated and the overall incidence of adverse events was similar between the ICRT group and ICT group. One patient in ICRT group stopped immunotherapy because of severe immune-associated pneumonia. 3.1% of grade 3-4 radiation-related adverse events were observed. Conclusions: Adding radiotherapy to first-line PD-1 inhibitors immunotherapy and chemotherapy improved outcomes of patients with advanced NSCLC and showed acceptable toxicity. Additional prospective studies exploring the first-line combination of immunochemotherapy and radiotherapy are warranted.