This article identifies and operationalizes the newly defined construct of attachment injury. An attachment injury occurs when one partner violates the expectation that the other will offer comfort and caring in times of danger or distress. This incident becomes a clinically recurring theme and creates an impasse that blocks relationship repair in couples therapy. An attachment injury is characterized by an abandonment or by a betrayal of trust during a critical moment of need. The injurious incident defines the relationship as insecure and maintains relationship distress because it is continually used as a standard for the dependability of the offending partner. The concept of an attachment injury is defined here in the context of emotionally focused therapy, an empirically validated, short-term approach to modifying distress in couples. The broad theoretical underpinnings of this concept may be found in attachment theory as applied to adult romantic relationships. Through the delineation of attachment injury events and the ongoing development of a detailed model of resolution, couples therapists will be better able to identify, describe, and effectively treat such injuries and address the therapeutic impasses that are associated with them.