Introduction. In the modern theory and practice of the functioning of foster families, there is a contradiction between recognizing the prolongation of the process of socio-psychological adaptation of foster family members and underestimating the asynchrony of its components. The purpose and novelty of the study was to identify the most “vulnerable” of them at the active stage of co-adaptation. Theoretical analysis. The analysis of scientific sources allowed us to conclude that the complexity of socio-psychological co-adaptation is related to the problem of the parity of its main components, the specifics of their meaningful characteristics for foster children and parents. This is particularly acute at the initial stage of the formation of substitute child-parent relations, which made it possible to introduce a clarifying term into the scientific field – co-adaptation of foster family actors and to identify a new perspective on the problem. Empirical analysis. The motivation of foster parents and foster children corresponds to a sufficiently high level of need for a family as a platform for successful socialization, development and formation of stable attachment relationships. The revealed significant differences in the cognitive component reflect the difference in expectations – in children they are focused on a certain past and an indefinite future, while in adults they are focused on a stable present and a visible perspective. The communicative-behavioral component reflects the dominant problems in establishing the parity of foster family actors. Conclusion. Correlations between the main components of socio-psychological co-adaptation have been identified, the significance and non-significance of which concretizes the possibility of positive dynamics in the future.