Internalizing ideals of thinness has been related to disordered eating. Thus, it is important to identify potential protective factors that may allow someone to internalize this belief without developing an eating disorder. In this study, we explored psychological flexibility and inflexibility as potential moderators of the relationship between thin-ideal internalization and disordered eating. College women (N = 201) completed the Multidimensional Psychological Flexibility Inventory, the thin-ideal internalization subscale of the Sociocultural Attitudes Towards Appearance Questionnaire, and the Eating Attitudes Test. Psychological inflexibility, but not psychological flexibility, was found to be a significant moderator of the relationship between thin-ideal internalization and disordered eating. Further analyses found that the specific subscales which moderated this relationship were Fusion, Lack of Present Moment Awareness, Lack of Values, and Inaction. Contrary to our hypothesis, disordered eating was positively related to Acceptance. The results suggest that being psychologically inflexible is particularly problematic in the context of thin-ideal internalization. Additionally, increasing acceptance may not be effective if the accepted thoughts are about the importance of thinness.