Background: Immune checkpoint inhibitors (ICIs), such as programmed death(ligand)1 (PD-(L)1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, have dramatic effects on treatment in patients with various malignancies. High tumor mutation burden (TMB) is predictive of clinical response to ICI in multiple cancer types. Although age-related immune dysfunction might induce difference on the efficacy of ICIs between younger and older patients, the potential effect of age on the efficacy of ICIs remains little known and controversial. Herein, we aimed to analysis the association between age and the efficacy of ICIs based on MSKCC cohort. Methods: We screened out 1661 patients having complete information with advanced cancer, whose tumors underwent next-generation sequencing (NGS) detection and who were treated with at least one dose of ICI in MSKCC cohort. All patients were divided into two groups according to age, the younger group (age ≤50-year old) and the older group (age > 50-year old). We further analyzed the differences in overall survival (OS) and TMB between the two groups. The pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated via Cox regression model for OS and P-values were calculated via the Wilcoxon sign test for TMB. We analyzed the effect of age on ICI in lung cancer using the same way. Results: In 1661 patients with cancer in our study, 312 (19%) younger and 1349 (81%) older patients were found. The pooled HRs for OS was 1.28 (95% CI: 1.09-1.52) in younger group compared with older group. In 1661 patients with cancer, there was 350 (21%) patients with lung cancer, including 30 (9%) younger and 320 (91%) older patients. The pooled HRs for OS was 1.45 (95% CI: 0.95-2.23) in younger group compared with older group in lung cancer. In addition, TMB in older group was higher than in younger group and significant difference of TMB was found via the Wilcoxon sign test (p = 2.6e-10) between the two groups, especially in lung cancer (p = 1e-4). Conclusions: Our study assessed the impact of age on the efficacy of ICIs using the threshold of 50 years old for the first time and we founded that patients in older group had higher TMB and longer OS than younger group.