The Alternative Lengthening of Telomeres (ALT) is a DNA damage repair process that is highly dependent on homologous recombination (HR). ALT?facilitates the synthesis of telomeric DNA through DNA repair mechanisms, which is represented by the appearance of a variety of hallmarks, including the accumulation of replication stress, upregulation of SUMO-dependent ALT associated PML bodies (APBs), and dynamic chromatin remodeling. Most cancers use telomerase to extend their telomeres, while approximately 10%-15% of telomerase-negative tumors maintain telomere length by initiating ALT pathway independent of telomerase. Unlike tumor cells, the vast majority of somatic cells gradually shorten their telomeres during division and proliferation due to low or absent telomerase activity, and this shortening is thought to ultimately trigger replicative senescence. Interestingly, it has found that the process of cellular senescence is also accompanied by ALT features, such as the accumulation of replicative stress and increases of APBs. It suggests that there may be some common regulatory mechanisms between senescent cells and telomerase-negative tumors. Although the telomere length in senescent cells is not effectively prolonged, ALT may be a potential mechanism for senescent cells to escape senescence and thus tumorigenesis. In this review, we summarize our knowledge on the association between telomerase-negative tumors and senescent cells. Finally, the context of this review elucidates the potential mechanisms of ALT in regulating cellular senescence and tumorigenesis, which provids potential targets and strategies for the treatment of telomerase-negative tumors in clinical practice.