Social support is one of many interpersonal functions that is impaired among individuals with bulimia nervosa. The buffering hypothesis of social support posits that social support shields the deleterious impact of stress on bulimic behaviors. However, the specific mechanism by which social support protects against the negative impact of stress on bulimic symptoms remains to be clarified. To investigate this mechanism, two studies examined the potential role of cognitive appraisal as a mediator in the relationship between social support and bulimic behaviors among undergraduate students. Study 1 was a longitudinal, naturalistic study in which participants completed online surveys at two assessment points that were four weeks apart. Bootstrap analyses revealed that cognitive appraisal did not mediate the relationship between perceived social support and bulimic behaviors. Exploratory analyses demonstrated that perceived stress, a construct parallel to cognitive appraisal with the emotional experiences taken into consideration, acted as a mediator in this relationship. Perceived social support appeared to be associated with decrease future bulimic behaviors through lowered stress perception. Study 2 was an experimental study that examined the role of cognitive appraisal in the relationship between social support and food consumption, which was used as a laboratory analogue of binge eating. Female participants were randomly assigned into one of two groups: with or without social support available. Stress was induced with a speech task, followed by a bogus taste task. Results demonstrated that perceived stress, instead of cognitive appraisal mediated the relationship between subjective ratings of the experimenter’s supportiveness and calories consumed. Unexpectedly, perceived supportiveness was associated with more caloric consumption through lower stress perception among individuals with high restraint. These studies extended the existing literature by examining perceived social support, perceived stress, and bulimic behaviors in a mediation model. Findings have theoretical and clinical implications for the role of social support in bulimic behaviors and the stress-disordered eating relationship. For example, stress does not always predict binge eating. Moreover, findings suggest the importance of social support in stress management and eating disorder treatments as well as the potential for emotional interventions for eating disorders.