Aim: The aim of the study was to define the patterns of attachment in adults with foetal alcohol syndrome from foster, adoptive and biological families. It was assumed that adults with foetal alcohol syndrome develop insecure attachment styles to a greater extent compared to the general population. Material and methods: Two groups of 30 people participated in this two-stage research. In the first stage, foetal alcohol syndrome was diagnosed in children using the University of Washington 4-Digit Diagnostic Code for foetal alcohol spectrum disorders. During the second stage, attachment style of young adults was assessed with the Polish version of the Experience in Close Relationships-Revised questionnaire. Furthermore, in-depth interviews were conducted with the parents or caregivers of individuals with foetal alcohol syndrome at both stages. In order to compare research results, a control group of 30 young adults with excluded foetal alcohol syndrome was formed. Results: Adults diagnosed with foetal alcohol syndrome achieved high scores in insecure attachment where a significant role is played by avoidant attachment and the fear of building close relationships. The degree of secure attachment in persons with foetal alcohol syndrome is markedly higher compared to the general population. Findings showed that in terms of attachment prototypes, the preoccupied type was prevalent (40%) and was followed by secure type (27%), and dismissing-avoidant type (23%) in the foetal alcohol syndrome group, whereas secure style dominated (61%) in the control group, and it was followed by the preoccupied (21%) and avoidant (13%) styles. Conclusions: The research showed that insecure attachment styles based on avoidance and anxiety dominate in adults diagnosed with foetal alcohol syndrome, which can cause disorders in creating bonds. Difficulties with developing close relationships in adults with foetal alcohol syndrome may significantly decrease the quality of their lives.