The current chapter systematically reviewed literature on online mindfulness interventions. Electronic databases were searched from 2005 to July 2016. The aim was to examine the nature of online mindfulness interventions, design features, and their effectiveness in improving symptoms of depression, anxiety, and stress. The review of selected studies shows that online delivery of mindfulness psycho-education and practice is an area in its infancy. There is evidence that online mindfulness interventions can have a positive impact on mental health in terms of stress, depression, and anxiety; however, large sample studies are needed in order to have conclusive results. Moreover, the extension of online mindfulness interventions beyond the individual level to include a community dimension, such as virtual community features, and a focus on the social determinants of health, needs to be explored in future. The online mindfulness intervention could be a cost-effective way to scale up the promotion of mental wellbeing.