Children with medical complexity (CMC) are a unique and challenging population in healthcare, characterized by substantial family-identified service needs, severe chronic conditions, functional limitations, and high health care utilization. Despite their significant impact on health outcomes, family well-being, and the healthcare system, there is a lack of well-characterized clinical initiatives and research efforts dedicated to improving their care. This article presents a definitional framework for CMC, consisting of four domains: needs, chronic conditions, functional limitations, and health care use. It explores existing care models and suggests a research agenda that uses a uniform definition to accurately describe the population and evaluate outcomes from the perspectives of the child, family, and healthcare system. The authors propose a clinical agenda based on the principles of the chronic care model, emphasizing family-centered care, enhanced coordination, and improved self-management. They also highlight the need for advocacy and system reform to prioritize CMC in healthcare policies and practices.Children with medical complexity (CMC) are a unique and challenging population in healthcare, characterized by substantial family-identified service needs, severe chronic conditions, functional limitations, and high health care utilization. Despite their significant impact on health outcomes, family well-being, and the healthcare system, there is a lack of well-characterized clinical initiatives and research efforts dedicated to improving their care. This article presents a definitional framework for CMC, consisting of four domains: needs, chronic conditions, functional limitations, and health care use. It explores existing care models and suggests a research agenda that uses a uniform definition to accurately describe the population and evaluate outcomes from the perspectives of the child, family, and healthcare system. The authors propose a clinical agenda based on the principles of the chronic care model, emphasizing family-centered care, enhanced coordination, and improved self-management. They also highlight the need for advocacy and system reform to prioritize CMC in healthcare policies and practices.