Implementation and sustainment of evidence-based interventions (EBIs) is influenced by outer (e.g., broader environments in which organizations operate) and inner (e.g., organizations, their administrators, and staff) contexts. One important outer-context element that shapes the inner context is funding, which is complex and unpredictable. There is a dearth of knowledge on how funding arrangements affect sustainment of EBIs in human service systems and the organizations delivering them, including child welfare and behavioral health agencies. This study uses qualitative interview and focus group data with stakeholders at the system, organizational, and provider levels from 11 human service systems in two states to examine how stakeholders strategically negotiate diverse and shifting funding arrangements over time. Study findings indicate that, while diverse funding streams may contribute to flexibility of organizations and possible transformations in the human service delivery environment, a dedicated funding source for EBIs is crucial to their successful implementation and sustainment.