Care coordination is central to health care delivery system reform efforts to control costs, improve quality, and enhance patient outcomes, especially for individuals with complex medical and social needs. The potential impact of addressing health-related social needs further illustrates the importance of coordinating health care services with community-based organizations that provide social services and support. This study offers early findings from a unique approach to care coordination delivered by 17 Medicaid Accountable Care Organizations and 27 partnering community-based organizations for individuals with behavioral health conditions and/or those needing long-term services and supports. Interview data from 54 key informants were qualitatively analyzed to understand factors affecting cross-sector integrated care. Key themes emerged, essential to implementing the new model statewide: clarifying roles and responsibilities; promoting communication; facilitating information exchange; developing workforce capacity; building essential relationships; and responsive, supportive program management through real-time feedback, financial incentives, technical assistance, and flexibility from the state Medicaid program.