Families with neurodevelopmental disorders engage in varied types and intensities of therapies to address behavioural, communication and cognitive challenges. Research suggests that consistent practice predicts positive therapy outcomes. The present study examined therapy adherence in 55 parent-child dyads where all children had been diagnosed with ASD, ADHD and/or ID. Parents completed questionnaires assessing demographics, therapy type and intensity, adherence to child treatment, parental stress, and challenging child behaviour. The researchers proposed a new scale, the Child Therapy Adherence Scale (CTAS), which initial testing supported as a reliable measure of therapy adherence. Significant relationships were found between parental stress, annual household income, and therapy adherence, with parental stress being a notably strong predictor of therapy adherence. No significant relationships were observed between child challenging behaviour, single parent status, and therapy adherence. These findings have implications for practitioners, in that parent and demographic influences may impact capacity to adhere to recommended home practice and interventions for children with neurodevelopmental disorders.