Comorbid anxiety and mood disorders are common but the majority of treatments tend to focus on a particular diagnosis. Previous research has found that cognitive behavioural therapy (CBT) targeted at a specific diagnosis can lead to improvements in comorbidities, especially in the case of CBT for panic. However, there is an emerging evidence base that transdiagnostic CBT, which addresses common underlying processes across presenting problems, may be effective at treating comorbidities simultaneously. Given the simple nature of the cognitive formulation of panic it is arguable that a panic-specific CBT intervention could help socialize patients to CBT before progressing to a transdiagnostic approach. This paper uses a single-case experimental design to illustrate an example of using diagnosis-specific CBT as a springboard to transdiagnostic CBT with a patient presenting with panic and agoraphobia, social anxiety, depression, uncontrollable worry, suicidality, self-harming behaviours and a history of bulimia. Results suggest that this was a well-received and effective intervention. Clinical implications are discussed as well as limitations and directions for future research