BACKGROUND: A major barrier to the widespread dissemination of psychological treatments is the way that therapists are trained. The current method is not scalable. OBJECTIVE: Our objective was to conduct a proof-of-concept study of Web-centered training, a scalable online method for training therapists. METHODS: The Irish Health Service Executive identified mental health professionals across the country whom it wanted to be trained in a specific psychological treatment for eating disorders. These therapists were given access to a Web-centered training program in transdiagnostic cognitive behavior therapy for eating disorders. The training was accompanied by a scalable form of support consisting of brief encouraging telephone calls from a nonspecialist. The trainee therapists completed a validated measure of therapist competence before and after the training. RESULTS: Of 102 therapists who embarked upon the training program, 86 (84.3%) completed it. There was a substantial increase in their competence scores following the training (mean difference 5.84, 95% Cl -6.62 to -5.05; P