Make a Difference (MAD) is a sustainability leadership program for high school students in Auckland, New Zealand. It offers a residential camp and follow-up activities. This article documents a participatory, utilization-focused evaluation of MAD, based on a Theory of Change approach. We ran workshops with MAD coordinators and students and conducted a survey with previous participants. This identified the core developmental and action outcomes of MAD, and the role of transformation and action competence in inspiring change. We discuss the benefits and limitations of both MAD and our evaluation approach and offer recommendations for others working on youth sustainability programs.