international masters games
event management
constraints
supplemental tourism activities
sport tourism
Supplemental tourism activities will be key in increasing sport event participants’ sense of satisfaction as well as economic impact. Therefore, the purpose of this study was to examine constraints to supplemental tourism activities among Japanese outbound sport tourists. A semi-structured interview was conducted with 23 Japanese participants at the Asia Pacific Masters Games 2018 Penang. The interview results identified 73.9% (n = 17) of the participants did not engage in supplemental tourism activities by experiencing masters-games-specific constraints, particularly event management. Poor event management (e.g., uncertain game schedules) resulted in a lack of time for their supplemental tourism activities. Our findings indicated that improving event management (e.g., notifying participants of game schedules in advance, keeping the schedules on time) is necessary for the World Masters Games 2021 Kansai to promote participants’ supplemental tourism activities. Furthermore, research on supplemental tourism activities across various sport events is needed for the development of sport tourism.