Background: Research on post-event processing (PEP), where individuals conduct a post-mortem evaluation of a social situation, has focused primarily on its relationship with social anxiety. Aims: The current study examined: 1) levels of PEP for a standardized event in different anxiety disorders; 2) the relationship between peak anxiety levels during this event and subsequent PEP; and 3) the relationship between PEP and disorder-specific symptom severity. Method: Participants with primary DSM-IV diagnoses of social anxiety disorder (SAD), obsessive compulsive disorder (OCD), panic disorder with/without agoraphobia (PD/A), or generalized anxiety disorder (GAD) completed diagnosis specific symptom measures before attending group cognitive behavioural therapy (CBT) specific to their diagnosis. Participants rated their peak anxiety level during the first group therapy session, and one week later rated PEP in the context of CBT. Results: The results indicated that all anxiety disorder groups showed heightened and equivalent PEP ratings. Peak state anxiety during the first CBT session predicted subsequent level of PEP, irrespective of diagnostic group. PEP ratings were found to be associated with disorder-specific symptom severity in SAD, GAD, and PD/A, but not in OCD. Conclusions: PEP may be a transdiagnostic process with relevance to a broad range of anxiety disorders, not just SAD.