© 2015, Society of General Internal Medicine. Background: Reducing patient cost-sharing and engaging patients in disease management activities have been shown to increase uptake of evidence-based care. Objective: To evaluate the effect of employer purchase of a disease-specific plan with reduced cost-sharing and disease management (the Diabetes Health Plan/DHP) on medication adherence among eligible employees and dependents. Design: Employer-level “intent to treat” cohort study, including data from eligible employees and their dependents with diabetes, regardless of whether they were enrolled in the DHP. Setting: Employers that contracted with a large national health plan administrator in 2009, 2010, and/or 2011. Participants: Ten employers that purchased the DHP and 191 employers that did not (controls). Inverse probability weighting (IPW) estimation was used to adjust for inter-group differences. Intervention: The DHP includes free or low-cost medications and physician visits. Enrollment strategies and specific benefit designs are determined by the employer and vary in practice. DHP participants are notified up front that they must engage in their own health care (e.g., receiving diabetes-related screening) in order to remain enrolled. Main Outcome Measure: Mean employee adherence to metformin, statins, and ACE/ARBs at the employer level at one year post-DHP implementation, as measured by the proportion of days covered (PDC). Results: Baseline adherence to the three medications was similar across DHP and control employers, ranging from 64 to 69 %. In the first year after DHP implementation, predicted employer-level adherence for metformin (+4.9 percentage points, p = 0.017), statins (+4.8, p = 0.019), and ACE/ARBs (+4.4, p = 0.02) was higher with DHP purchase. Limitations: Non-randomized, observational study. Conclusions: The Diabetes Health Plan, an innovative health plan that combines reduced cost-sharing and disease management with an up-front requirement of enrollee participation in his or her own health care, is associated with a modest improvement in medication adherence at 12 months.