The World Health Organization estimates that during a given 12-month period, approximately 34 million people suffering from major depressive disorder go untreated in Europe and the Americas alone. Barriers to treatment include geographic distance, lack of mental health insurance, prohibitive cost of treatment, long wait-lists, and perceived stigma. Over the past two decades, Internet-based cognitive-behavioral therapy (iCBT) programs have proliferated. A growing body of research supports the efficacy of iCBT for depression and other psychiatric conditions, and these programs may help address barriers that hinder access to effective treatment. The present review describes common iCBT programs along with the evidence base supporting their efficacy in reducing symptoms of depression, reviews research on moderators of treatment response, and provides suggestions for future directions in research and care.