Parents of children with Autism Spectrum Disorder are responsible for deciding which interventions to implement with their child. There is limited research examining parental decision-making with regards to intervention approaches. A constructivist grounded theory methodology was implemented in this study. Semi-structured interviews were undertaken with 14 participants from 12 family units. Data collection and analysis occurred concurrently, allowing a grounded theory to be constructed. Parental decision-making was influenced by many factors, arranged into seven core categories (values, experience, information, motivation, understanding, needs and logistics). Decision-making evolved over time, as parents transformed from 'parent' to 'expert'. The results of this study provide an insight into parental decision-making, which has implications for the support provided to parents by health professionals.