This study investigated the flow experience of open-water swimmers and how it influencestheir event identification andfavorability toward a sponsor. This study also examined the potential moderating effect of a sponsor's brand experience on the relationship between the swimmer's positive affect and attitude toward the sponsoring brand. A total of 344 survey questionnaires were collected from participants in the ”28th International Swimming across Sun Moon Lake Carnival.” The results of partial least square analysis indicated that flow experience generates a positive swimmer affect, leading to a stronger event identification and sponsor favorability. In addition, the sponsor's brand experience moderates, to an extent, the relationship between a swimmer's initial positive affect and his or her sponsor favorability. This paper emphasizes the importance of developing the flow experience of open-water swimmers and offers managerial insights for both event organizers and sponsors.