OBJECTIVE: This randomized controlled trial evaluated the efficacy of Primary Care Stepping Stones Triple P, a brief individualized parenting program, in a sample of parents of children with autism spectrum disorder (ASD). METHOD: Sixty-four parents of children aged 2-9 years (M = 5.67, SD = 2.14) with an ASD diagnosis participated in the study. Eighty-six percent of children were male, and 89% of parents identified their child's ethnicity as Australian/White. Families were randomly assigned to 1 of 2 conditions (intervention or care-as-usual) and were assessed at 3 time points (preintervention, postintervention, and 6-month follow-up). Parents completed a range of questionnaires to assess changes in child behavior (Eyberg Child Behavior Inventory) and parent outcomes (Parenting Scale, Depression Anxiety Stress Scale-21, Parent Problem Checklist, Relationship Quality Inventory, Parental Stress Scale) and 30-min home observations of parent-child interactions. RESULTS: Relative to the care-as-usual group, significant short-term improvements were found in the intervention group on parent-reported child behavior problems, dysfunctional parenting styles, parenting confidence, and parental stress, parental conflict, and relationship happiness. No significant intervention effects were found on levels of parental depression or anxiety, or on observed child disruptive and parent aversive behavior. The effect sizes for significant variables ranged from medium to large. Short-term effects were predominantly maintained at 6-month follow-up, and parents reported high levels of goal achievement and satisfaction with the program. CONCLUSIONS: The results indicate that a brief low intensity version of Stepping Stones Triple P is an efficacious intervention for parents of children with ASD.