Peer education is an understudied yet valuable strategy for sustainability educators in shifting youth to take action for sustainability. This case study conceptualizes the change process in facilitating youth to take sustainability actions, and explores the benefits, dynamics, and challenges of peer education as a strategy in facilitating change. It assesses the learning of youth leaders of the "MindShift" program, and the extent to which they took action. Findings reveal multifaceted learning related to various antecedents of sustainability actions. The most influential elements of the peer education approach were peer support, meaningful contribution, teaching/leadership role, and student ownership.