Transdiagnostic models of anxiety, and cognitive-behavioral treatments based on these models, have been gaining increased attention in recent years. Preliminary efficacy studies generally suggest strong treatment effects, although few of these studies have examined to what extent treatment effects are similar across clients with different anxiety disorders. The purpose of the current study was to examine the efficacy of a 12-week transdiagnostic group cognitive-behavioral therapy for anxiety disorders and compare outcome across diagnoses. Mixed-effect regression modeling of data from 52 participants with anxiety disorders (predominantly panic disorder and social phobia) participating in an open outcome trial indicated that participants tended to improve over treatment, with no differential outcome for any primary or comorbid disorders. The results of this study add to the growing evidence base for transdiagnostic anxiety treatment models and provide preliminary support for the assumption that individuals with different anxiety diagnoses can be treated equally within the same treatment protocol.