ObjectivesDyadic peer support helps patients make health behavior changes for improved outcomes, yet the impact of matching dyads on demographic characteristics such as race or gender is unknown. Therefore, we investigated associations of concordant characteristics with peer outcomes in a diabetes prevention intervention and qualitatively examined participant perspectives on matching. MethodsBinary variables for peer-supporter concordance on 6 demographic characteristics were created for 177 peers and 69 supporters. Regression models compared changes in weight, HbA1c, perceived social support, patient activation, and formal diabetes prevention/education program participation for concordant and non-concordant dyads. Semi-structured qualitative interviews were conducted with 39 peers and 34 supporters. ResultsConcordance on demographic characteristics was not significantly associated with outcomes. Qualitatively, peers and supporters emphasized that more important than shared demographic characteristics was a supporter's empathic, non-judgmental communication style. ConclusionsDemographic characteristics for matching supporters with adults with prediabetes are less important than ensuring high-quality coach training in goal setting and communication style, supporting prior research on the necessity of autonomy supportive communication for effective behavioral change interventions. Practice implicationsExisting peer support programs should incorporate fidelity assessments into practice to ensure peer supporter skill in motivational interviewing-based, autonomy supportive communication and brief goal setting.