Attachment and attachment-related psychopathology has increasingly gained focus since Bowlby introduced the concept into the clinical repertoire. However, little has been done to explore attachment, or attachment-based interventions, within the context of intellectual disability. Clinical experience, however, has demonstrated significant attachment-related problems in children with intellectual disability. This article explores one such case of a 13-year-old girl with moderate intellectual disability and severe and persistent externalizing behavioural difficulties--biting, in particular. Once the severity of the behaviour was formulated within the framework of attachment, a structured attachment-focused parent-child intervention was designed in order to repair the damaged attachment between mother and daughter as a way of addressing the problematic behaviour. Outcomes demonstrated a sustained--immediately, at 3- and 6-month follow-up--positive impact of the intervention not only on the presenting problem but also on the quality of the relationship between mother and daughter. Research and clinical implications are discussed.