The off-label use of medicines is widespread in several diseases. This type of prescribing practice is particularly more acute in oncology. However, the suitability of anticancer medications for off-label use remains an issue of controversy, due to uncertainty around the clinical benefits and potential toxicities, limited evidence to support clinical decision-making, increased out-of-pocket costs for patients and ethical concerns around the lack of informed consent. Currently, data pertaining to the global prevalence of off-label use in cancer therapy are lacking. The aim of this review was to provide an overview of off-label drug use prevalence in oncology.