Chronic pancreatitis (CP), is a long-term inflammation of the pancreatic parenchyma, and might increase risk of a hyperglycemia crisis or hypoglycemia in patients with diabetes mellitus (DM); however, the relationship has not been previously investigated. To investigate the risk of diabetic ketoacidosis (DKA), hyperglycemic hyperosmolar state (HHS), hypoglycemia, and long-term outcomes in DM patients with CP. A population-based cohort study. Tapping Taiwan's National Health Insurance Research Database, we identified 506 DM patients with newly diagnosed CP from 1999 to 2010 and created a control cohort consisting of 5060 age- and sex-matched DM patients without CP from the same time period. We followed those 2 cohorts from the index date to occurrence of outcomes, the date of death or 31 December 2012. DKA, HHS, hypoglycemia and mortality. DM patients with CP, who were predominantly male (88%) and younger (60% < 45 years old), had a 9.5-, 5.0-, and 3.0-fold higher risk for DKA (95% confidence interval [CI]: 6.51-13.91), HHS (95% CI: 2.85-8.62), and hypoglycemia (95% CI: 2.23-4.08), respectively. They also had lower 1-, 5-, and 10-year cumulative survival rates (98.4% vs 99.0%, 87.7% vs 96.6%, and 78.7% vs 93.6%, respectively) (log-rank test: P < .001), and a 2.43-fold higher risk for death (HR: 2.43, 95% CI: 1.82-3.27). In Taiwan, DM patients with CP have a higher incidence of DKA, HHS, hypoglycemia, and mortality. More attention is needed for preventing hyperglycemia crisis and hypoglycemia prevention in this population.