AimsTo evaluate retention and outcomes of insured adults with prediabetes who enrolled or did not enroll in National Diabetes Prevention Programs (NDPPs). MethodsBetween 2015 and 2019, 776 University of Michigan employees, dependents, and retirees with prediabetes and overweight or obesity enrolled in one-year NDPPs. ResultsEnrollees attended a median of 18 sessions. Median retention was 38 weeks. Retention was associated with older age, greater initial weight loss, and physical activity. At both 1- and 2-years, body mass index, triglycerides, and HbA1c were significantly improved among enrollees. After adjusting for age group, sex, and race, the odds of developing diabetes based on HbA1c ≥6.5 % was 40 % lower at 1-year and 20 % lower at 2-years, and the odds of self-reported diabetes was 57 % lower at 1-year and 46 % lower at 2-years in enrollees compared to non-enrollees. Enrollees who disenrolled before completing the core curriculum had higher odds and enrollees who completed the NDPP had lower odds of developing diabetes that non-enrollees. ConclusionsIn this population with prediabetes, NDPP retention was generally good, risk factors were improved, and diabetes was delayed or prevented for up to two years.