Hawaii’ s Honolulu Marathon, first held in 1973, has become an international mega sports event. December 2011’ s Honolulu Marathon registered 22,615 participants from all over the world, including 12,360 Japanese runners. Hawaii is one of the most popular tourist destinations for Japanese tourists, and participants in the Honolulu Marathon enjoy being tourists as well as marathoners. While there is a voluminous academic literature on the motivation and constraints associated with sports events participation, only a few authors have examined participant motivation or constraints in terms of international sports events. This study examines participant motivation and constraints as both marathoner and tourist. Data were gathered from 218 participants (107 participants in 2010 and 111 participants in 2011) in the Japan Tourist Bureau’ s Honolulu Marathon tour, and subjected to factor analysis. Five sports motivations (running involvement, socialization, self-development, excitement, commitment to the Honolulu Marathon) , five tourist motivations (escape, relaxation, culture learning, shopping & gourmet, kinship with family and friends) , and five constraints (marathon event information, tourist information, companions, safety & culture differences, and financial issues) were extracted from explanatory factor analysis (EFA) . Some differences in terms of each factor were observed in relation to demographics such as gender or age category, in particular, factors related to tourist motivations. The Structural Equation Model (SEM) showed that further intention was significantly affected by the interest in the Honolulu Marathon as a sports motivation factor, kinship in terms of tourist motivation factor, and marathon information as a constraint factor. It also demonstrated that their satisfaction was significantly influenced by marathon interest, excitement and tourist information. These results not only provide an insight into the Honolulu Marathon’ s event management planning, but also demonstrate the extraordinary brand value this event has among Japanese participants.