This study evaluates the effectiveness of California’s Whole Person Care (WPC) initiative in coordinating health and social services for Medicaid beneficiaries with complex needs during the COVID-19 pandemic. Projects underway in 26 counties engage Medicaid health plans, medical providers, mental health agencies, social service organizations, and public health agencies in collaborative models of care and payment that target specific population groups with complex needs in each county, including people experiencing homelessness, those transitioning from incarceration, and patients with multiple chronic medical conditions. Using a quasi-experimental research design, researchers assess changes in collaborative community networks, service delivery patterns, and patient outcomes for program participants and matched comparison groups across 26 county-level projects before and after the onset of the COVID-19 pandemic. The study analyzes data from network surveys, Medicaid claims data, and key-informant interviews to assess program effectiveness from multiple perspectives. Researchers from the University of California-Los Angeles and University of California-Berkeley are collaborating with the California Department of Health Care Services to conduct the study.