The link between cancer and diabetes is established but not fully understood. Incretin-based therapies have been increasingly used in the past decade for management of type 2 diabetes mellitus (T2DM). A link between incretin pathway and cancer has been supposed but a debate in the scientific committee is rising whether incretin-based therapies have beneficial or harmful effects on patients with malignant diseases or at risk of malignancy. This review summarizes the published preclinical and clinical research discussing incretin-based therapies and cancer. Except for pancreatic cancer, thyroid cancer, and cholangiocarcinoma, the published data agree that incretin-based therapies have either a beneficial or zero effect on risk of malignancy. Regarding pancreatic cancer, there are case reports of pancreatic cancer after receiving incretin-based drug therapy but the lag time for tumorigenesis is questionable. Till date, meta-analyses agreed that no increased incidence of pancreatic cancer was observed among users of incretin-based therapies. Whether incretin-based therapies increase the risk of thyroid cancer is controversial therefore it is advisable to avoid prescribing glucagon-like peptide-1 receptor agonists (GLP-1RAs) for patients with high risk for thyroid cancer. Despite the numerous studies published about incretins and cancer, it is still a rich area for further research.