The rising global demographic aging and the subsequent increase in the prevalence of age-related diseases highlight the need to understand aging biology. A key player in organismal aging is the immune system, which has broad systemic effects. On the one hand, immune aging involves the decline of hematopoietic stem cells and significant alterations in the functionality and composition of both innate and adaptive immunity. On the other hand, the aged immune system contributes to chronic inflammation and disrupted tissue homeostasis, thereby driving systemic aging processes. In this review, we examine the close interaction between aging and the immune system and discuss emerging therapeutic strategies aimed at modulating immune function to mitigate age-related pathologies.