Between 2004 and 2007, Girls Incorporated conducted research about the experience of five affiliates from different parts of the United States as they engaged with girls in Girls Study Girls Inc., a participatory evaluation project that explored the meaning and impact of Girls Inc. environments and uncovered ways such environments can be improved. We describe the context and motivation for using participatory action research [PAR] in Girls Inc. environments and discuss the relevance and importance of PAR for organizations that empower girls and young women. We explain the process of training and engaging Girls Inc. members in research, discuss the effectiveness of Girls Study Girls Inc. as an evaluation strategy, and conclude this article with lessons learned and recommendations for using PAR in evaluating youth development programs.