AbstractThe relationship between diabetes mellitus (DM) and pancreatic cancer is complex—DM is both a risk factor and early sign of pancreatic cancer. DM is a risk factor for pancreatic cancer because it increases insulin resistance, intrapancreatic concentrations of insulin, and the bioavailability of IGF, subsequently promoting ductal cell proliferation. Accordingly, treatment targeting the insulin/IGF pathway is the focus of many researchers. Antidiabetic drugs modify the risk for pancreatic cancer—metformin's antineoplastic effect being most notable and indicating potential clinical use in pancreatic cancer. New-onset DM can also be the first manifestation of pancreatic cancer. There are several theories for the pathogenesis of DM in pancreatic cancer, the most important being that DM is a paraneoplastic syndrome caused by diabetogenic factors. As a consequence of this intricate relationship, new-onset DM after the age of 50 is considered a red flag for pancreatic cancer, prompting the need for screening in this patient population. Multiple clinical studies are currently underway exploring this matter. A better understanding of the relationship between DM and pancreatic cancer could aid in developing novel screening and treatment strategies for pancreatic cancer. This could ultimately improve the prognosis and quality of life of patients with pancreatic cancer.