The impending climate crisis creates a critical need to understand the complex social phenomena of human behaviour for the purpose of meaningful interventions to support and foster sustainable practices. Using a qualitative case study approach, the annual Earth Day Festival (the Festival) in the rural community of Roberts Creek, British Columbia, is examined for its supporting effect on pro-environmental behaviour (PEB). Using grounded theory, the research finds six themes identified as place, education, community, support, practice, and celebration. These themes, when mapped onto the belief, normative and control constructs of the Theory of Planned Behaviour, demonstrate how the Festival successfully influences PEB at the individual and community levels. Explored also are three unique properties of the Festival that further support PEB change. These are diversity of experience, interconnection of interventions, and the supportive feedback of celebration. These properties emerge from the combination and interaction of the six themes.