Despite its name, discovery history and approval as anticancer agent, tumor necrosis factor (TNF) has been implicated in both cancer development and progression in some preclinical models. In particular, as a central mediator of inflammation, TNF might represent one of the molecular links between chronic inflammation and the subsequent development of malignant disease. Furthermore, deregulated TNF expression within the tumor microenvironment appears to favor malignant cell tissue invasion, migration and ultimately metastasis formation. On the other side, TNF clearly possesses antitumor effects not only in preclinical models but also in the clinical setting. In order to reconcile these conflicting findings, we provide readers with an overview on the most relevant available evidence supporting anticancer as well as cancer-promoting TNF effects; on the basis of these data, we propose a model to explain the coexistence of these apparently paradoxical TNF activities.