This dissertation investigated the role of youth-led participatory action research (YPAR) in influencing decision-making in five California public health departments. To my knowledge, this is the first systematic study of the utilization of YPAR for decision-making in public health, or in any other field. The present study employs qualitative methods, using a case study approach in multiple sites. Data sources include in-depth interviews, document review and participant observation. The two conceptual frameworks within the research utilization literature that guide this study are the decision-making model and frames of reference. I examined how YPAR projects fit existing models of research utilization and compared the utilization of YPAR compared to traditional research across all five departments in public health department decision-making. I found that the utilization of YPAR in the decision-making of the public health departments fit the political, problem-solving and interactive models. A key finding is the utility of YPAR to decision-makers. Decision-makers are more likely to use YPAR when it is action oriented and relevant to their work. There is also evidence that departments who do not traditionally use research are utilizing YPAR to drive policy change in their communities on issues that impact young people. It appears to provide additional utility to public health department decision-making that traditional research may not provide. Strengths, limitations and implications of this study for future study of YPAR and decision-making are also presented.