Postevent processing (PEP) is proposed to be a key maintenance factor of social anxiety disorder (SAD; e.g., Clark and Wells 1995). The goal of the current study was to examine the independent roles of two transdiagnostic variables, namely perfectionism and intolerance of uncertainty (IU), as unique predictors of PEP in SAD above and beyond social anxiety and depressive symptoms. Fifty-six adults with SAD and high levels of speech anxiety completed measures of perfectionism, IU, social anxiety, and depression. They gave an impromptu speech to induce PEP, and completed measures assessing degree of PEP and its associated distress. Significant positive correlations were found between perfectionism and negative PEP degree and distress, as well as between IU and negative PEP distress. The perfectionism subscales of parental expectations and parental criticism significantly predicted negative PEP degree and distress over and above social anxiety and depressive symptoms. Perfectionism, as well as IU, were significantly and positively correlated with positive PEP distress, and significantly predicted positive PEP distress above and beyond social anxiety and depressive symptoms. The study design was cross-sectional; hence, experimental and longitudinal studies are needed to further understand the roles of perfectionism and IU as they relate to PEP. Individuals with SAD who are high in perfectionism or IU appear to be more prone to engaging in, or experiencing distress associated with, negative PEP. Specific strategies for decreasing negative PEP in this vulnerable population, especially for those high in perfectionism, may be necessary for optimal treatment outcome.