Using a cross-lagged panel design, we investigated the impact of positive family processes on change in autism symptoms and behaviors. A sample of 149 co-residing mothers and their adolescent or adult child with autism was drawn from a large, longitudinal study. Maternal warmth and praise were measured using coded speech samples in which mothers talked about their son or daughter. A high level of relationship quality was associated with subsequent reductions in internalizing and externalizing problems as well as reductions in impairments in social reciprocity and repetitive behaviors. Maternal warmth and praise were also related to symptom abatement in the repetitive behaviors domain.