Limited access to evidence-based behavioral parent training (BPT) for addressing attention deficit/hyperactivity disorder (ADHD) has been a growing concern internationally. Models to improve access to BPT are needed, particularly those that can be readily implemented in community settings and that leverage the potential workforce to increase capacity to deliver BPT. The purpose of this study was to evaluate a BPT model which included oft-used content, methods, processes of BPT (common-elements), non-professionally delivered (task-shifted/shared) BPT intervention, and an efficient ancillary support system (training, fidelity, and supervision methods) for families of youth with parental concerns about ADHD. In a randomized controlled trial of 161 families of children (79% male; mean age 7.04 [1.55]), the Caring in Chaos (CiC) BPT model, delivered by community volunteers across 12 community-based sites in Denmark, was compared to a wait-list control condition on key child and parent outcomes at immediate post-treatment and 4-month follow-up assessment points. Results suggested that the CiC model led to significantly greater improvement in parenting behavior, parenting sense of competence, child functional impairment, parental stress and parental depressive symptoms compared to the wait list condition at immediate post-treatment, with maintenance of gains in most of these areas at follow-up assessment. No effect of intervention was found on ADHD symptoms. The results of this study suggest that developing efficient BPT intervention models, such as the CiC model, can result in readily implemented interventions by a variety of individuals in community settings. Such models are necessary to bend the curve on addressing unmet needs of families of youth with concerns about ADHD.