P Natural killer (NK) cells function as crucial effectors in the innate immune response against tumors. Nevertheless, NK cell senescence, characterized by phenotypic and functional changes, substantially compromises their antitumor immune response. This review provides a comprehensive summary of the molecular mechanisms governing NK cell senescence and its implications for cancer immunotherapy. We propose a refined definition of NK cell senescence based on distinct biomarkers, including elevated CD57 expression, reduced cytotoxicity, and altered cytokine secretion. Moreover, we investigate the complex interactions between the tumor microenvironment (TME) and NK cell senescence, highlighting the influence of chronic inflammation, immunosuppressive cytokines, and persistent tumor antigenic stimulation. Additionally, this review underscores the potential utility of senescent NK cells as biomarkers for assessing antitumor efficacy and examines the adverse effects of NK cell senescence on cancer immunotherapy. Lastly, we summarize current approaches to mitigate NK cell senescence, such as gene editing techniques and cytokine modulation, which may enhance the efficacy of NK cell-based immunotherapies. By establishing a comprehensive framework for understanding NK cell senescence within the TME, this review aims to guide future research and the development of innovative therapeutic strategies targeting senescent NK cells to improve cancer immunotherapy outcomes.