OBJECTIVES Immunotherapy is a therapeutic agent that stimulates the immune system and induces immune cells to selectively attack only cancer cells. This study aim to compare efficacy and safety profiles among atezolizumab which are PD-L1 inhibitors, nivolumab and pembrolizumab, which are PD-L1 inhibitors. METHODS In this study, We retrospectively evaluate the objective response rate (ORR) and the progression-free survival (PFS) of patients 65 years of age or older who received atezolizumab, nivolumab, or pembrolizumab from September 1, 2018 to December 31, 2020 at the Veterans Health Service (VHS) Medical Center in Seoul, South Korea. Adverse reactions were studied in all patients who received immunotherapy at least once, based on the records of the electronic medical record. RESULTS The objective response rate (ORR) was 20% among 40 patients in the atezolizumab group, 23.8% among 80 patients in the nivolumab group, and 31.3% among 48 patients in the pembrolizumab group. (P = 0.449). The study involving only NSCLC(Non-small-cell lung carcinoma) patient, 9.4% among 32 patients in the atezolizumab group, 19.35% among 31 patients in the nivolumab group, and 33.3% among 48 patients in the pembrolizumab group. (P = 0.057). Hazard ratios of nivolumab vs. atezolizumab on PFS was 0.65 (95%. CI 0.41-1.02, p=0.063), pembrolizumab vs. atezolizumab was 0.63 (95%, CI 0.37-1.07, p=0.087) and pembrolizumab vs. nivolumab was 0.97 (95%, CI 0.61-1.56, p=0.9098). In the NSCLC patients, nivolumab vs. atezolizumab was 0.50 (95%. CI 0.27-0.92, p=0.027), pembrolizumab vs. atezolizumab was 0.43 (95%, CI 0.23-0.81, p=0.008) and pembrolizumab vs. nivolumab was 0.87 (95%, CI 0.44-1.72, p=0.689).CONCLUSIONS : There was no statistically significant difference on ORR and PFS between atezolizumab, nivolumab, and pembrolizumab. However, when only NSCLC patients were targeted, nivolumab and pembrolizunab showed effective results compared to atezolizumab.