Children with autism spectrum disorder (ASD) vary greatly in social functioning, and in turn, long-term relational and academic outcomes. Responsive parenting which follows a child's lead and focus of attention is predictive of language and social gains for children with or without developmental risk. The present study prospectively assessed 176 families of children with ASD (ages 4 to 7 years) to examine predictors of observed responsive parenting and associations of responsive parenting with concurrent and prospective growth in social functioning by multi-method assessment. Responsive parenting concurrently associated with child characteristics (IQ, language, sex) and child social engagement within the interaction. Structural equation models revealed that responsive parenting positively predicted prospective growth in social skills by teacher but not parent report.