Children's mental health services have been revolutionized to reflect the realization that youth with mental health needs are served by multiple service sectors, including child welfare, juvenile justice, special education, primary health care, mental health, and alcohol and drug services. Systems of care models have attempted to improve integration of services across these multiple sectors and have been influential in driving policy and funding changes, but these models have focused primarily on cross-sectional service use. The goal of this conceptual article is to expand on these models by identifying factors that affect dynamic, longitudinal multi-sector service use. Greater understanding of these longitudinal patterns may suggest effective targets for intervention. In addition, this conceptual framework may provide a contextual template for current studies of multi-sector service need, use, and effectiveness.