Given the putative importance of maladaptive self-beliefs in cognitive models of social anxiety, there is growing interest in the construct’s influence on social anxiety reduction in treatment. The present study sought to examine whether maladaptive self-beliefs reduce over a 12-week course of cognitive behavioural therapy (CBT) for social anxiety disorder (SAD), and whether change in self-beliefs is an indicator of later change in social anxiety symptom severity within treatment. Participants were 77 individuals with SAD who completed measures of maladaptive self-beliefs every 2 weeks of the treatment protocol and measures of social anxiety each week. Using a dynamic bivariate latent difference score framework, results indicated that maladaptive self-beliefs reduced during CBT for SAD, and that change in maladaptive self-beliefs was a significant predictor of later change in social anxiety symptom severity. Reductions in social anxiety was not a significant predictor of later change in self-beliefs. Findings underscore the importance of maladaptive self-beliefs in the maintenance of social anxiety and in treatment for SAD. Moreover, they permit inferences about the temporal sequence of change processes in therapy and are consistent with CBT therapeutic models suggesting that cognitive change precedes symptom change.