Theory and evidence suggest the potential value of prodromal intervention for infants at risk of developing autism. We report an initial case series (n = 8) of a parent-mediated, video-aided and interaction-focused intervention with infant siblings of autistic probands, beginning at 8–10 months of age. We outline the theory and evidence base behind this model and present data on feasibility, acceptability and measures ranging from parent-infant social interaction, to infant atypical behaviors, attention and cognition. The intervention proves to be both feasible and acceptable to families. Measurement across domains was successful and on larger samples promise to be an effective test of whether such an intervention in infancy will modify emergent atypical developmental trajectories in infants at risk for autism.