Environmental consciousness has become increasingly important in the professional sports industry as it often hosts large-scale events that have significant environmental impacts. While the economic benefits of locating stadiums in city centers have been discussed, especially in terms of neighborhood revitalization, there has been limited empirical research on whether stadium relocation affects the transportation choices of spectators and reduces carbon dioxide emissions. Through a case study of a Japanese professional football club that relocated its home stadium from the suburb to the city center, this study quantitatively elucidated the change in spectators’ transportation choices and resulting reductions in carbon emissions achieved by the stadium relocation. Analysis indicated variations in behavioral changes among groups based on their loyalty levels to the club. It also highlighted the varying influence of the different residential areas within the metropolitan area on the modal choice. This study demonstrates the potential contribution of stadium relocation to sustainable urban planning by providing empirical evidence of these behavioral changes and policy implications for restructuring the urban public transportation network.