Background: ICIs have changed the treatment paradigm in many cancer histologies. Population-level data regarding the impact of ICIs on the contemporary US cancer patients is scarce. In addition, elderly patients were underrepresented in the landmark trials. Methods: Metastatic cancers (melanoma, lung cancer, kidney cancer, head and neck cancer, Hodgkin’s lymphoma, and urothelial cancer) diagnosed between 2004-2018 were identified in the Surveillance, Epidemiology, and End Results (SEER) database. The year of the first FDA approved ICI in each cancer site was considered the commencement of the ICI era. The impact of metastatic cancers diagnosed in the ICI era was assessed in each age group (<65, 65-75, and ≥75) using multivariable Cox regression after adjustment for age, sex, race, household income and residence status (metropolitan vs non-metropolitan) Results: There were 363,191 patients with metastatic cancers included in the analysis [lung cancer: 68%, head and neck cancer: 14%, Hodgkin Lymphoma: 7%, kidney cancer: 7%, urothelial cancer: 3%, and melanoma: 2%): 60% were male and 73% were non-Hispanic White. The median age was 66 (interquartile range: 57-75). After baseline adjustments for sociodemographic factors, metastatic cancers diagnosed in the ICI era had improved overall survival except urothelial cancer (Table). Results of overall survival and cancer-specific survival were consistent across all age groups (<65, 65-75, and ≥75). Among patients with age ≥75, metastatic cancers diagnosed in the ICI era had improved overall survival in melanoma (AHR: 0.81, p-value<.0001), lung cancer (AHR:0.91, p-value<.0001), kidney cancer (AHR: 0.89, p-value: 0.0004), head and neck cancer (AHR:0.82, p-value<.0001), Hodgkin lymphoma (AHR: 0.75, p-value:0.003) but not in urothelial cancer. Conclusions: Metastatic cancers diagnosed in the ICI era had improved overall survival and cancer-specific survival including the subgroup of age ≥ 75. ICIs should not be withheld in elderly patients solely due to chronological age.