Participatory evaluation is a form of citizen science that brings program stakeholders into partnership with researchers to increase the understanding and value that evaluation provides. For the last four years, 4-H volunteers and staff have joined academics to assess the impact of the California 4-H camping program on youth and teen leaders in areas such as responsibility, confidence and leadership. Volunteers and nonacademic staff in the field informed the design of this multiyear impact study, collected data and engaged in data interpretation through “data parties.” In a follow-up evaluation of the data parties, we found that those who participated reported deeper understanding of and buy-in to the data. Participants also provided the research team insights into findings. By detailing the California 4-H Camp Evaluation case study, this paper describes the mutual benefits that accrue to researchers and volunteers when, through data parties, they investigate findings together.