Policy makers are increasingly investing in programs focused on identifying and addressing the nonmedical needs of high-utilizing Medicaid beneficiaries, yet little is known about these programs' implementation. This study provides an overview of early progress in and strategies used to implement California's Whole Person Care (WPC) Pilot Program, a $3 billion Medicaid Section 1115(a) waiver demonstration project focused on improving the integrated delivery of health, behavioral health, and social services for Medicaid beneficiaries who use acute and costly services in multiple service sectors. WPC pilots reported significant progress in developing partnerships, data-sharing infrastructure, and services needed to coordinate care for identified patient populations. We also identified major barriers to WPC implementation, such as difficulty identifying and engaging eligible beneficiaries and the lack of affordable housing. Our findings offer insights to leaders and policy makers interested in testing new approaches for improving the health and well-being of medically and socially complex patients.