Whilst the Triple P Positive Parenting Program has a large evidence base (Sanders, Clinical Child and Family Psychology Review 2:71-90, 1999; Sanders, Journal of Consulting and Clinical Psychology 68:624-640, 2000) and preliminary evidence indicates that Stepping Stones Triple P is also efficacious (Roberts, Journal of Clinical Child and Adolescent Psychology, 35(2):180-193, 2006), to date Stepping Stones has not been evaluated with the ASD population. Fifty-nine families with a child with ASD aged between 2 and 9 participated in this randomized controlled trial. The results demonstrate significant improvements in parental reports of child behaviour and parenting styles with the treatment effects for child behaviour, parental over reactivity and parental verbosity being maintained at follow-up 6 months later. Further, the results suggest significant improvements in parental satisfaction and conflict about parenting as well as a sleeper effect for parental efficacy. The results indicate that Stepping Stones Triple P is a promising intervention for parents of children with ASD. Limitations and future research are also addressed.