Recently, there has been growing interest in stress and coping strategies from a relational perspective. Researchers recognize the importance of a partner's coping strategy in terms of relationship satisfaction and a relational sense of well-being. The aim of the article is to present the results of work on the Polish validation of the Dyadic Coping Inventory (DCI), which was developed by Bodenmann (2008). Dyadic coping is a multidimensional construct which consists of stress communication by partners and four components of dyadic coping behavior: supporting, delegated, negative and common behavior. The DCI examines the quality of communication between partners and the level of dyadic coping with stress. The DCI was tested based on a study of 550 people (275 couples) aged between 20 and 72. The conducted analyses were aimed at checking the factor structure and psychometric properties of the Polish version of the DCI. Measurement invariance (MI) was also tested across genders on a Polish sample and across cultures on Polish, Swiss and Romanian samples. After rejection of three pairs of items, factor analysis of the DCI revealed a 5-factor structure with respect to a partner’s own dyadic coping and their partner’s dyadic coping and a 2-factor structure with respect to common dyadic coping. MI results confirmed the criteria for configural, metric and full scalar invariance across genders and configural, metric and partial scalar invariance across cultures. The Polish version of DCI has satisfactory psychometric characteristics and can be used to assess the dyadic coping of people in romantic relationships; also, it can be used in cross-cultural studies.