Interleukin-7 (IL-7) is a cytokine that has been known since long in immunology, mainly regarding its effects on T-cells and B-cells. IL-7 has been demonstrated to be necessary for both B-cell and T-cell proliferation and lack of IL-7 causes immature immune cell arrest. Interestingly, in recent years, certain studies have strongly suggested that the role of IL-7 is far beyond the field of immunology, it might have direct or indirect effect on cancer. This review aims to summarize the role of IL-7 in immunity and its role in the pathogenesis of neoplasia.