Our perception of emotion in the faces of others affects our own behavior and mood. Indeed, individuals with mood disorders such as depression and aggression often show biases in facial-emotion perception. Here, we review recent and ongoing research suggesting that biased emotion perception may be on the causal pathway of the onset and maintenance of mood disorders, and hence a potential target for intervention. Simple cognitive-bias modification tasks that change participants’ perception of facial expressions of emotion have shown some promise as a therapeutic technique. We outline further directions for continued research investigating the robustness and clinical impact of emotion-bias modification in real-world settings.