Two dimensions of perfectionism related to eating disorder (ED) symptoms are evaluative concerns and high standards. Evaluative concerns are consistently linked with ED symptoms, whereas there are conflicting results regarding high standards and ED symptoms. High standards are unrelated to ED symptoms in some studies and are linked to higher ED symptoms in others. Intolerance of uncertainty (IU) may influence the relation between high standards and ED symptoms; individuals elevated in both IU and high standards may find it distressing to be uncertain about future situations for fear of not living up to high expectations and use ED behaviors to cope with such uncertainty. In the current study (N = 216), we explored whether IU moderates the relationships between high standards and evaluative concerns and ED symptoms, both cross-sectionally and prospectively across two weeks. IU significantly moderated high standards and ED symptoms both cross-sectionally and across time while accounting for baseline ED symptoms, but did not moderate the relationship between evaluative concerns and ED symptoms. Higher standards were associated with greater ED symptoms in individuals higher, but not lower in IU. These findings suggest high standards may only contribute to ED symptoms when individuals are also high in IU.