The Social ABCs is a parent‐mediated intervention for toddlers with suspected or confirmed autism spectrum disorder (ASD). We undertook a multi‐site pilot study to evaluate feasibility and acceptability, and to identify trends in child and parent behavior to inform future research using a larger sample and a rigorous research design. The program involved 12 weeks of parent coaching, followed by 12 weeks' implementation, and 3‐month follow‐up assessment for 20 parent‐toddler dyads (age range: 12–32 months). Parents successfully learned the techniques and rated the intervention as highly acceptable. Paired samples t‐tests revealed significant gains in children's functional communication (responsivity, initiations), and language gains (age‐equivalents on standardized measures) commensurate with typical developmental rates. Significant increases in shared smiling and social orienting also emerged, but were attenuated at follow‐up. Parents' fidelity was positively associated with child responsivity. Training parents as mediators is a feasible and highly acceptable approach that provides a potentially cost‐effective opportunity for intensive intervention at a very young age at the first signs of ASD risk. Child and parent gains in several key variables demonstrate the promise of this intervention. Autism Res 2016, 9: 899–912. © 2015 The Authors Autism Research published by Wiley Periodicals, Inc. on behalf of International Society for Autism Research