There is an urgent need to develop and evaluate effective and scalable interventions to prevent or delay the onset of type 2 diabetes mellitus (T2DM). In this randomized controlled pragmatic trial, 296 adults with prediabetes will be randomized to either a peer support arm or enhanced usual care. Participants in the peer support arm meet face-to-face initially with a trained peer coach who also is a patient at the same health center to receive information on locally available wellness and diabetes prevention programs, discuss behavioral goals related to diabetes prevention, and develop an action plan for the next week to meet their goals. Over six months, peer coaches call their assigned participants weekly to provide support for weekly action steps. In the final 6 months, coaches call participants at least once monthly. Participants in the enhanced usual care arm receive information on local resources and periodic updates on available diabetes prevention programs and resources. Changes in A1c, weight, waist circumference and other patient-centered outcomes and mediators and moderators of intervention effects will be assessed. At least 296 participants and approximately 75 peer supporters will be enrolled. Despite evidence that healthy lifestyle interventions can improve health behaviors and reduce risk for T2DM, engagement in recommended behavior change is low. This is especially true among racial and ethnic minority and low-income adults. Regular outreach and ongoing support from a peer coach may help participants to initiate and sustain healthy behavior changes to reduce their risk of diabetes. The ClinicalTrials.gov registration number is NCT03689530.