With rapidly rising rates of mental health disorders, changing patterns of occurrence, and increasing levels of morbidity, the need for a better understanding of the developmental origins and influence of mental health on children’s behavioral health outcomes has become critical. This need for better understanding extends to both the growing prevalence of mental health disorders as well as the role and impact of neurodevelopmental pathways in their onset and expression. Addressing these changes in disease patterns and effects on children and families will require a multifaceted approach that goes beyond simply making changes to clinical care or adding personnel to the health services system. New policies, financing, and implementation can put established best practices and numerous research findings from around the country into action. The Maternal and Child Health Life Course Intervention Research Network and the Forum for Children's Well-Being at the National Academies of Sciences, Engineering, and Medicine jointly organized a webinar series to explore how mental health disorders develop over the life course, with a special emphasis on prenatal, early, middle, and later childhood development. This series centered on identifying gaps in our knowledge, exploring possible new strategies for using existing data to enhance understanding of the developmental origins of mental disorders, reviewing potential approaches to prevention and optimization, and proposing new ways of framing how to understand, address, and prevent these disorders from a life course development perspective. This publication summarizes the presentations and discussions from the series.