Up to one third of patients with chronic hepatitis C virus (HCV) develop type 2 diabetes mellitus (DM). This prevalence is much higher than that observed in the general population, and in patients with other chronic liver diseases such as hepatitis B virus, alcoholic liver disease, and primary biliary cirrhosis. Further, HCV seropositivity in patients with DM appears to be higher than in the general population. Post- liver transplantation DM also appears to be higher among patients with HCV. In this article, we review the epidemiologic association between HCV and DM, highlighting the most recent pathophysiologic insights into the mechanisms underlying this association.