The article presents the theoretical aspects of the use of attachment theory in group psychotherapy. In the literature, we can find a lot of research and publications regarding the use of this concept to understand individual and family psychotherapy, but less frequently in group psychotherapy. As it seems, this perspective can be useful for the understanding of the individual functioning of particular participants, the group process or the effectiveness of group psychotherapy, depending on the attachment style. Recent years have shown a growing interest in the implications of this concept to understanding group treatment, but further research is very necessary in this area. Although the article refers mainly to attachment in adulthood described in two dimensions – avoidance and anxiety, as well as to attachment styles known as secure, preoccupied, dismissive/avoiding or fearful/disorganized, the first part presents the basics of Bowlby’s attachment theory, which has formed the basis for further conceptions. Next, we considered the understanding of group psychotherapy phenomena and possibilities of formulating therapeutic interventions based on attachment theory. In part two of the article, empirical studies on the use of attachment theory in group psychotherapy were reviewed.