Cognitive behavioral therapy (CBT) has been found to be very effective in reducing many forms of mental illness, but much less is known about whether CBT also promotes mental health or well-being. The goals of the present study were to (a) quantify the magnitude and timing of changes in overall well-being and specific facets of well-being during different CBTs for anxiety disorders, (b) determine whether these effects vary across transdiagnostic and disorder-specific CBT, and (c) examine how changes in well-being during treatment relate to changes in anxiety. A total of 223 adults (55.6% female, Mage = 31.1 years) were randomized to 1 of 5 CBT protocols for anxiety disorders at an outpatient clinic. Analyses included standardized mean gain effect sizes (ESsg) and latent growth curve modeling. Moderate-to-large increases in overall well-being and the 3 components of subjective, psychological, and social well-being were observed, mainly during the second half of CBT, and these increases were maintained at a 6-month follow-up. The magnitude of effects was comparable for transdiagnostic and disorder-specific CBT protocols and greater than in the waitlist condition. Parallel process latent growth curve models indicated that trajectories of change in well-being across treatment were strongly correlated with trajectories of change in clinician-rated and self-reported anxiety. Together, these findings suggest that different CBT protocols for anxiety consistently produce robust and lasting changes in well-being, and these changes are strongly linked to changes in anxiety during treatment. (PsycInfo Database Record (c) 2020 APA, all rights reserved).