Food waste from institutional food services accounts for a significant part of global food waste. Food waste sorting (FWS) at the source reduces waste management costs and environmental impacts in organizations. Yet what drives individual FWS behavior remains underexplored. This study explores the psychological process of FWS in institutional catering environments, integrating the value-belief-norm model, the theory of planned behavior, and self-determination theory. Data were collected from 431 university students in China and analyzed using partial least squares structural equation modeling (PLS-SEM). Results indicated the interplay of values, beliefs, norms, and motivations in shaping FWS behaviors. Social value orientations (SVO) indirectly affected FWS through awareness of consequences and personal norms. Subjective norms, potentially attributed to external regulations in canteens, influenced FWS intention through personal norms and induced FWS primarily via controlled motivations. The findings imply that behavioral strategies to induce FWS may leverage social influence and external regulation while also translating values and knowledge into intrinsic motivations through educational programs and awareness campaigns.