This study examines relationships between emotion beliefs and emotion regulation strategy use among people with social anxiety disorder (SAD) and a psychologically healthy control group. Using experience-sampling methodology, we tested group differences in 2 types of emotion beliefs (emotion control values and emotion malleability beliefs) and whether emotion beliefs predicted trait and daily use of cognitive reappraisal and emotion suppression. People with SAD endorsed higher emotion control values and lower emotion malleability beliefs than did healthy controls. Across groups, emotion control values were positively associated with suppression (but unrelated to reappraisal), and emotion malleability beliefs were negatively associated with suppression and positively associated with reappraisal. We also addressed 2 exploratory questions related to measurement. First, we examined whether trait and state measures of emotion regulation strategies were related to emotion control values in different ways and found similar associations across measures. Second, we examined whether explicit and implicit measures of emotion control values were related to daily emotion regulation strategy use in different ways-and found that an implicit measure was unrelated to strategy use. Results are discussed in the context of growing research on metaemotions and the measurement of complex features of emotion regulation. (PsycInfo Database Record (c) 2021 APA, all rights reserved).