Abstract: Rapid population aging has significantly increased tumor incidence. Immunotherapies, particularly immune checkpoint inhibitors (ICIs) and CAR-T cell therapy, represent core treatment strategies. However, older patients frequently experience challenges with these therapies, including unpredictable efficacy, variable response rates, and poor tolerance. Immunosenescence likely contributes significantly to these limitations. This review analyzes immunosenescence characteristics and elucidates how it modulates tumor progression and treatment response through tumor microenvironment remodeling and altered immune cell function. By examining treatment response heterogeneity among older patients across cancer types, this review proposes immunosenescence-targeted sensitization strategies to optimize immunotherapy response rates and safety in this population.