This chapter explores the association between intimate relationship functioning and psychopathology. It begins with a review of the literature on intimate relationship functioning and how it is correlated with the prevalence and incidence of psychopathology, focusing on the results of cross-sectional and longitudinal studies. It then considers the literature on couple-based interventions as treatments for specific forms of psychopathology such as mood disorders, substance use disorders, posttraumatic stress disorder (PTSD), obsessive-compulsive disorder, and anorexia nervosa. The chapter focuses on three couple-based interventions, namely, cognitive-behavioral couple therapy, emotion-focused couple therapy, and strategic approaches to couple therapy. It concludes by outlining directions for future research to better understand the link between intimate relationship functioning and psychopathology.