Diffusion theory posits that information is disseminated throughout a social network by the persuasion of key opinion leaders (KOLs). This study examined the relative and combined influence of peer-identified KOL teachers (n = 12) and mental health providers (n = 21) on classroom teachers' (n = 61) self-reported use of commonly recommended classroom practices for children with attention-deficit/hyperactivity disorder in 6 low-income urban African American communities, relative to teachers (n = 54) at 4 matched schools who received mental health provider consultation only. Mixed-effects regression models showed that KOLs in collaboration with mental health providers promoted higher rates of teachers' self-reported use of recommended strategies than mental health providers alone, and that these effects were mediated by KOL support but not by mental health provider support. The results suggest an expanded role for KOL teachers as indigenous and natural supports for the dissemination and implementation of school-based mental health programs.