This review examines the application of online interventions to the treatment of obesity. The unprecedented prevalence rates of overweight and obesity worldwide are indicative of the need to develop efficacious treatment alternatives. While research suggests that diet, physical activity and behaviour therapy are core components of effective obesity treatment programs, their ability to penetrate large portions of the population is limited. The empirically verified effectiveness of online interventions for disorders such as depression and social phobia, coupled with unparalleled rates of internet access, suggest that online interventions for overweight and obesity are a feasible and logical treatment modality. A limited number of randomised controlled trials reviewed in this article have evaluated the efficacy of this treatment alternative. Results are promising and encourage further use, development and empirical research in this area.