Background: Immune checkpoint inhibitor (ICI) plus chemotherapy is now a standard treatment for non-small cell lung cancer (NSCLC) without targetable oncogene alternations. However, the efficacy and safety of ICI plus chemotherapy (ICI-chemo) in 75 years or older patients have not been elucidated. The aim of this study is to reveal the real-world choice of first-line drugs in elderly patients (pts) and evaluate the efficacy and safety of ICI-chemo. Methods: We conducted a multicenter (58 centers in Japan), retrospective cohort study of consecutive 75 years or older pts with clinical stage IIIB, IIIC, IV, postoperative or radiotherapy recurrent NSCLC who started first-line systemic therapy between December 2018 and March 2021. Pts with epidermal growth factor receptor mutations, anaplastic lymphoma kinase rearrangements, or whose first-line systemic therapy was molecular targeted therapy were excluded. Results: A total of 1245 pts were enrolled: median (range) age 78 (75-95) years; 278 (22%) female; 367 (29%) ECOG PS 0, 680 (55%) PS 1 and 171 (14%) PS 2; 678 (54%) adenocarcinoma; PD-L1 tumor proportion score 268 (22%) <1%, 387 (31%) 1-49% and 410 (34%) ≥50%; 354 (28%) ICI-chemo, 425 (34%) ICI alone, 311 (25%) platinum-doublet chemotherapy and 155 (12%) single agent chemotherapy. The median overall survival (OS) was 20.0 months (95%CI, 17.1–23.6) in the ICI-chemo group, 19.8 months (95%CI, 16.5–23.8) in the ICI alone group, 12.8 months (95%CI, 10.7–15.6) in the platinum-doublet chemotherapy group and 9.5 months (95%CI, 7.4–13.4) in the single agent chemotherapy group, respectively. After propensity score matching, there was no difference in OS and progression-free survival (PFS) between ICI-chemo group (n=96) and ICI alone group (n=95) in PD-L1 ≥1% (OS: HR, 0.98; 95% CI, 0.67-1.42, PFS: HR, 0.92; 95% CI, 0.67-1.25). Regardless of PD-L1 subgroups (1-49% or ≥50%), no significant differences in OS and PFS were observed. Concerning safety, Grade 3 or higher immune-related adverse events (irAEs) occurred in 86 pts (24.3%) in the ICI-chemo group and 76 pts (17.9%) in the ICI alone group (p = 0.03). The number of pts who required steroids for irAEs was 115 (32.5%) in the ICI-chemo group and 105 (24.7%) in the ICI alone group (p = 0.02). Pneumonitis was reported in 83 pts (23.4%) in the ICI-chemo group and 66 pts (15.6%) in the ICI alone group (p = 0.006). Conclusions: In real-world data for pts aged 75 years or older, ICI-chemo did not improve survival and increased the incidence of grade 3 or higher irAEs compared to ICI alone. Based on our results, ICI alone is recommended for elderly pts with PD-L1 positive NSCLC. Clinical trial information: UMIN000046700.