State health departments funded by the Centers for Disease Control and Prevention's Nutrition, Physical Activity, and Obesity Program collaborate with multiple partners to develop and implement comprehensive obesity prevention and control programs. A mixed-methods evaluation of 28 state programs over a 5-year period assessed states' progress on program requirements, including developing statewide partnerships and coordinating with partners to support obesity prevention and control efforts. States with greater partnership involvement leveraged more funding support for their programs, passed more obesity-related policies, and were more likely to implement obesity interventions in multiple settings. Case studies provided guidance for establishing and maintaining strong partnerships. Findings from this study offer emerging evidence to support assumptions about the centrality of partnerships to states' success in obesity program development and implementation and related health promotion activities.