Age is the most important risk factor for tumorigenesis. More than 60% of new cancers and more than 70% of cancer deaths occur in elderly subjects >65 years. The immune system plays an important role in the battle of the host against cancer development. Deleterious alterations occur to the immune response with aging, termed immunosenescence. It is tempting to speculate that this waning immune response contributes to the higher incidence of cancer, but robust data on this important topic are few and far between. This review is devoted to discussing state of the art knowledge on the relationship between immunosenescence and cancer. Emerging understanding of the aging process at the molecular level is viewed from the perspective of this increased tumorigenesis. We also consider some of the most recent means to intervene in the modulation of immunosenescence to increase the ability of the immune system to fight against tumors. Future research will unravel new aspects of the immune response against tumors which will be modulable to decrease the burden of cancer in elderly individuals.