The purpose of this study was to investigate the sustainable practices of nutrition science teachers and dietitians working in school food service operations, and identify the social and psychological factors which affect the overall efficacy of the system. The research model was constructed based on the Extended Theory of Planned Behavior (ETPB) in order to analyze how individual motivation affects the sustainable practices of nutrition science teachers and dietitians. The data were collected through e-mail and postal mail from nutrition science teachers and dietitians all across Korea, and self-administered surveys were conducted. SPSS and AMOS programs were used for statistical analysis. First, the sustainable practices of nutrition science teachers and dietitians were analyzed in 6 different categories. Second, the significant pathways were 6 out of 9 in the ETPB model. Sustainable food service practices in school can contribute to the formation of more a sustainable culture, such as through the encouragement of more healthy eating habits, and higher level of environmental awareness and community awareness. The factors influencing these practices can be applied to the design of improvement programs aimed at increasing sustainable practices.