Parent-mediated intervention can enhance parents' competence in supporting parent-child social interactions. Research and current policy have highlighted the importance of building family capacity in supporting parents to help children with autism develop social communication abilities. Parents who experienced parent-mediated interventions have reported reduced parenting stress; however, few studies have examined parents' learning outcomes from such interventions for children with autism. We assessed parents' learning outcomes from participation in the Joint Attention Mediated Learning (JAML) intervention and explored differences in parents' application of mediated learning principles between intervention and control groups. We used parent-child interaction videos to analyze parents' application of mediated learning principles with their toddlers in home settings and found significant group differences in parents' application of the principles at postintervention. Parents in the intervention group showed significant improvements in their competence in mediating child learning in unstructured parent-child interactions, but there were no significant gains for parents in the control group. [This article was published in "Topics in Early Childhood Special Education" (EJ1353898).]