This study used an actor¿partner interdependence analytic approach to examine a theoretical model assessing whether lower differentiation of self is linked to higher psychological distress and lower dyadic adjustment. Data from 195 heterosexual Spanish couples were analyzed. Results showed significant actor effects in all variables. Regarding partner effects, women¿s emotional cutoff had a significant influence on their partner¿s psychological distress and dyadic adjustment; however, men¿s emotional cutoff had a significant relationship with their partner¿s dyadic adjustment but not psychological distress. Emotional reactivity on the other hand, the intrapersonal dimension of differentiation of self, did not manifest any partner effect. The findings provide (a) a new approach on the role of differentiation of self in intra- and interpersonal distress; (b) cross-cultural support for previous research; and (c) an integrated model for a systemic understanding of these variables, grounded in a strong theoretical framework, which explained up to 62% of model variance. Overall, our results support Bowen¿s basic assumptions and systems theory principles that a couple is an emotional unit, and suggest that interventions targeting emotional cutoff may be particularly helpful to benefit both members of the couple. Other implications for therapy and suggestions for future research are discussed.