We present the case of an adult male ("Jake") with chronic Anorexia Nervosa, buttressed by dysfunctional levels of perfectionism and aggravated by long-standing mood and anxiety disturbance, successfully treated with Radically Open Dialectical Behavior Therapy (RO DBT). RO DBT is an evidence-based, transdiagnostic psychotherapy designed to address perfectionistic overcontrolled coping through teaching flexibility, openness, and healthy self-doubt. We illustrate this treatment approach by means of describing its application to this case, including discussing core RO DBT treatment strategies and providing sample dialogues. Also demonstrated are the importance of case conceptualization strategies specific to overcontrolled individuals, unique challenges with attending to alliance ruptures with this population such as difficulty discriminating when they occur, and the importance of prioritizing social signaling as a treatment target. Jake's Anorexia Nervosa was in remission at the conclusion of treatment.