Recent efforts have focused on developing and evaluating early intervention for toddlers with probable or emerging autism spectrum disorder. Parent-mediated approaches have gained traction, with mounting evidence of efficacy, but a research-to-practice gap exists, and community effectiveness remains to be firmly established. We report outcomes of a parent-mediated toddler intervention delivered through a research-community partnership, using a community-partnered participatory framework. Data were available for 179 of 183 toddler-parent dyads receiving Social ABCs parent coaching (mean toddler age: 25.18 months; range, 14-34 months). Of these, 89.4% completed the 12-week program and 70.6% returned for 3-month follow-up assessment. Parents attained implementation fidelity exceeding 75%, and toddlers made gains on proximal and distal measures of social communication. Parent fidelity was associated with toddlers' responsivity at week 12, and responsivity predicted later language gains and reduced autism spectrum disorder symptoms. The roles of child, family, and system factors are discussed. Community delivery of an evidence-based parent-mediated intervention for toddlers with autism spectrum disorder is feasible and effective. Given resource efficiencies associated with parent-mediated approaches, findings bolster current efforts to promote earlier and more widespread access to intervention at the first signs of developmental concern.