We investigated the cardiovascular complications and mortality rates of patients with diabetes in South Korea. The rates of hospitalization due to cardiovascular complications and mortality were analyzed using the Korean National Health Insurance Service-National Sample Cohort. From 2006 to 2015, the rates of hospitalization due to major cardiovascular complications decreased, while those due to heart failure (from 72 to 146 and 124 to 161 per 10,000 men and women, respectively) and peripheral artery disease (from 39 to 55 and 19 to 35 per 10,000 men and women, respectively) increased. In the period 2007 to 2015, the mortality rates for cancer, cerebrovascular disease, diabetes, heart disease, and hypertensive disease all decreased. However, the mortality rate for pneumonia increased. We observed a continuous reduction in cardiovascular complications and mortality in adults with diabetes. However, with the increase in some diabetes complications, more efforts are needed to prevent diabetes complications.