The study was a randomized controlled trial evaluating the efficacy of a brief and preventatively-focused parenting discussion group for dealing with disobedient behavior in preschool-aged children. Eighty-five parents with children aged between 3 and 5 years who were concerned about the noncompliant behavior of their child were recruited from Auckland, New Zealand and Brisbane, Australia. Compared to the waitlist control group (n = 40), parents in the intervention group (n = 45) reported greater improvements in disruptive child behavior, ineffective parenting practices and parenting confidence, as well as clinically significant improvements in child behavior and parenting. All of these effects were maintained at 6-month follow up. No group differences were found for parental wellbeing, inter-parental conflict and general relationship quality, although intervention parents reported improvements in parental wellbeing and inter-parental conflict at 6-month follow-up. The findings are discussed in terms of the implications for making brief and effective parenting support available to parents.