Interleukin-1 (IL-1) has long been known to be a key mediator of immunity and inflammation. Its dysregulation has been implicated in recent years in tumorigenesis and tumor progression, and its upregulation is thought to be associated with many tumors. Overexpression of the IL-1 agonists IL-1α and IL-1β has been shown to promote tumor invasiveness and metastasis by inducing the expression of angiogenic genes and growth factors. IL-1 blockers such as anakinra and canakinumab are already approved and widely used for the treatment of some autoimmune and autoinflammatory diseases and are currently being tested in preclinical and human clinical trials for cancer therapy. In this paper we review the most recent discoveries regarding the association between IL-1 dysregulation and cancer and present the novel IL-1 blockers currently being tested in cancer therapy and their corresponding clinical trials.