Obesity affects nearly one in five children in the United States and costs billions of dollars to manage and treat. National advisors and funding agencies are increasingly encouraging multiple sectors of society to work together on childhood obesity prevention, yet the extent to which states are adopting and succeeding with this approach is unknown. In this dissertation, I address this gap in the literature using national surveillance data and a mixed methods case study in Minnesota. In study 1, I examined secular trends and state-level political, social, and economic conditions associated with collaboration on school nutrition and physical education (PE) activities nationally. Collaboration increased between 2000 and 2006 and decreased or stabilized between 2006 and 2012. The number of organizational collaborators in 2012 was higher in states with higher childhood obesity prevalence, higher poverty, higher public health funding, and a state-level PE coordinator. In study 2, I examined the prevalence of evidence-based state policies on competitive foods and PE between 2006 and 2012. Findings from generalized linear models indicate that strong state policies were unrelated to measures of collaboration and significantly positively associated with childhood obesity and state-level measures of socioeconomic disadvantage in 2012. In study 3, I used mixed methods to develop a theoretically informed process to identify and describe the roles of key stakeholders in a Safe Routes to School (SRTS) partnership in Minnesota. The Minnesota partnership was successful in implementing SRTS programs in nearly 200 communities and advocating for policy change to expand and institutionalize SRTS in the state. Findings indicate that contributors to success of sophisticated partnerships may differ across multiple geographic levels and core partnership functions. Overall, the findings from this dissertation suggest that collaborative partnerships are common and under some circumstances, such as SRTS in Minnesota, may contribute to adoption and/or implementation of policies to prevent childhood obesity.