Couple distress is not only highly prevalent but also detrimental to individual emotional, behavioral, and physical well-being. Moreover, relationship problems can impede treatment response for a wide range of psychological disorders. Understanding couple distress requires that assessment extend beyond individual factors to include the broader relational and socioecological context. This chapter describes the multifaceted etiological considerations in couple assessment and provides brief screening measures and methods for the diagnosis of couple distress. Assessment techniques capable of evaluating behavioral, cognitive, and affective components of couple distress are highlighted. The chapter emphasizes the best practices in conceptualizing and assessing couple distress for the purpose of treatment planning and evaluation. Best practice recommendations and potential areas for future research are explicated.