Attachment Theory has received increasing interest as a framework allowing for a more refined understanding of the potential consequences of early relational trauma on psychological and social adjustment. Research has provided support for the role of disorganized attachment, both as a sequela of traumatic experiences and as a risk factor for subsequent maladjustment. This study investigated the associations between unresolved/disorganized attachment, cognitive functioning, and dissociative symptomatology in a sample of 60 adolescents with a history of maltreatment. A model with cognitive efficiency as a mediator variable was tested using hierarchical multiple regression analysis, with a bootstrapping procedure to examine indirect effects. Results provided support for the association between unresolved attachment, cognitive efficiency (but not verbal or thinking ability), and dissociation. Working memory was a strong mediator of the link between attachment and dissociation. These results highlight the importance of assessing attachment status and cognitive functioning in the context of clinical work with maltreated youth. In addition, it is proposed that greater attention be paid to internal models of attachment relationships and how they impact psychosocial functioning at different levels in maltreated populations.