Depression is one of the most common mental disorders today. Depression has a high recurrence rate, and may have a large negative impact on life-quality for the individual. This implies that treatment of depression should not only focus on treating a current depression, but should also focus on preventing new episodes. Biased attention toward negative information has been found in individuals with a current depression, but also in individuals in remission. Modifying this attentional bias with Attention Bias Modification (ABM) has been highlighted as a promising intervention to prevent depression relapse. The goal of ABM is to redirect attention toward a positive attentional bias, making the individual more attentive to positive stimuli. In this randomized controlled trial (RCT-study), 123 individuals with a history of depression executed ABM twice a day for two weeks (28 sessions). The participants were randomly assigned to an active or a placebo condition of ABM. Clinical, demographic and cognitive variables were assessed before ABM. Depressive symptoms were assessed both before and after ABM. An emotion regulation paradigm provided a measure of the emotion regulation strategy reappraisal within 3 weeks after ABM. Individuals in the active ABM condition showed a trend toward a greater decrease in depressive symptoms than individuals in the placebo condition after two weeks of ABM. There was no difference between the active ABM and placebo group in their ability to use reappraisal after ABM. The hypothesis that reappraisal mediate the relationship between ABM and depressive symptoms was not supported. The study carries indications that ABM may have a therapeutic effect on depressive symptoms for individuals at high risk of depression recurrence, but more research is needed to understand the mechanisms by how ABM works.