Several studies have shown that dyadic coping, that is, the way couples cope with stress, plays a unique role in intimate relationships. The aim of this study is to validate the Portuguese version of the Dyadic Coping Inventory (DCI; Bodenmann, 2008) by analyzing the factorial structure and psychometric properties of the DCI as well as its convergent and criterion validity. A multigroup confirmatory factor analysis was conducted in a community sample of 605 participants living in Portugal who had been in a close relationship for at least 2 years. The findings support the hypothesized five-factor structure for the DCI and self- and other-perception, and a two-factor structure for joint dyadic coping. The psychometric properties of the DCI and its criterion validity with other relationship measures (RAS and B-SRQ) were good. These results add an important contribution to the determination of the criterion validity of the DCI with measures of other crucial domains of couples’ functioning (Shared Meaning, Conflict Processes, and Quality of Sexuality, Passion, and Romance); to the cross-cultural validation of the DCI; and to the demonstration that negative DC has a significant effect on intimate relationship processes, which contradicts the findings of previous studies. Moreover, it provides an additional tool for working with Portuguese-speaking individuals all over the world.