Even if the participation of locals is limited in mega-event decision-making, their support is crucial to the event’s success. Using Social Exchange Theory, the study examines the extent to which community participation and perceived impacts affect residents’ support of mega-events. Implementing a structural model, the examination is based on the combination of two pieces of research undertaken before and after the London Olympics. Findings confirm the importance of perceived benefits and costs in community support. They also reveal the increase in positive perceptions after the event, the strengthening of community participation willingness and residents’ support, and provide an understanding of the role of perceived success in perspective formulation. Moreover, the study uses an explanatory model for the visualisation of the findings.