High-contact structured diabetes prevention programs are effective in lowering weight and HbA1cs, yet their intensity level can create barriers to participation. Peer support programs improve clinical outcomes among adults with Type 2 diabetes, but their effectiveness in diabetes prevention is unknown. This study examined whether a low-intensity peer support program improved outcomes more than enhanced usual care in a diverse population with prediabetes. The intervention was tested in a pragmatic 2-arm RCT. Participants were adults with prediabetes at 3 healthcare centers. Participants randomized to the enhanced usual care arm received educational materials. Participants in the Using Peer Support to Aid in Prevention and Treatment in Prediabetes arm were matched with a peer supporter: another patient who had made healthy lifestyle changes and was trained in autonomy-supportive action planning. Peer supporters were instructed to provide weekly telephone support to their peers on specific action steps toward behavioral goals for 6 months, then monthly support for 6 months. Changes in primary outcomes of weight and HbA1c and secondary outcomes of enrollment in formal diabetes prevention programs, self-reported diet, physical activity, health-specific social support, self-efficacy, motivation, and activation at 6 and 12 months were examined. Data collection occurred from October 2018 to March 2022, with analyses completed in September 2022. Among 355 randomized patients, in intention-to-treat analyses, there were no between-group differences in HbA1c or weight changes at 6 and 12 months. Using Peer Support to Aid in Prevention and Treatment in Prediabetes participants were more likely to enroll in structured programs at 6 (AOR=2.45, p=0.009) and 12 (AOR=2.21, p=0.016) months and to report eating whole grains at 6 (4.49, p=0.026) and 12 (4.22, p=0.034) months. They reported greater improvements in perceived social support for diabetes prevention behaviors at 6 (6.39, p<0.001) and 12 (5.48, p<0.001) months, with no differences in other measures. A stand-alone, low-intensity peer support program improved social support and participation in formal diabetes prevention programs but not weight or HbA1c. It will be important to examine whether peer support could effectively complement higher-intensity, structured diabetes prevention programs. This trial is registered at ClinicalTrials.gov, NCT03689530. Full protocol available at https://clinicaltrials.gov/ct2/show/NCT03689530.