Background Self‐concept is seen as both an outcome of sociocognitive and emotional development, and a factor in social and mental health outcomes. Although the contribution of attachment experiences to self‐concept has been limited to quality of primary attachment relationships, little is known of the effects of disturbed attachment on self‐concept in institutionalized children. Thus, the current study examined associations between disturbed attachment behaviours in institutionalized children and self‐concept, testing limited exploration as an explanatory factor. Methods Thirty‐three institutionalized children, aged 4–12, participated in a multimethod and multi‐informant assessment of disturbed attachment behaviours (i.e., Disturbances of Attachment Interview and Behavioral Signs of Disturbed Attachment in Young Children), self‐concept (i.e., Pictorial Scale of Perceived Competence and Social Acceptance for Young Children), and exploratory behaviours (i.e., Student Exploratory Behaviours Observation Scale). Analyses were conducted using bootstrapping techniques. Results Global self‐concept converged with teacher‐rated children's self‐concept, except for physical competence domain. Disturbed attachment behaviours were identified in 62.5% of the children, and this was associated with lower levels of exploration and lower scores on self‐concept, compared with children without disturbed attachment behaviours. Furthermore, exploratory behaviours mediated the effects of disturbed attachment behaviours on self‐concept. Conclusions Institution‐reared children with disturbed attachment behaviours were likely to have a negative perception of self and one's own competences. Limited exploratory behaviours explained this linkage. Targeting disordered attachment in children reared in institutions and their caregivers should become a high priority as a means for preventing socioemotional development issues.