Internet-assisted cognitive behavioral therapy (ICBT) is a way to deliver cognitive behavioral therapy (CBT) that has been found to generate similar effects as face-to-face CBT in some studies. Results have been replicated by different research groups. This article presents the treatment format and reviews evidence for mood and anxiety disorders. Future developments are discussed, including the lack of theories specific for the treatment format and ways to handle comorbidity. Although some programs have been implemented, there is a need for further studies in clinical settings. Overall, clinician-assisted ICBT is becoming one of the most evidence-based forms of psychological treatment.