Anorexia Nervosa (AN) is a severe and potentially chronic disorder characterised by low body weight and persistent behaviours that interfere with weight gain. Individuals with AN are often difficult to engage in treatment and display high rates of drop out. The Collaborative Case Conceptualisation (CCC) assessment approach was developed to target proposed AN maintaining factors with the aim of improving treatment motivation and engagement and consequently treatment outcomes in individuals with AN. The proposed study aims to examine the efficacy of CCC in improving a range of outcomes including Body Mass Index, eating disorder symptomatology, general psychopathology, quality of life and future treatment motivation and participation. Potential mediators will also be explored.Thirty-two participants will be recruited from Melbourne based specialist eating disorder services, community and university clinics, and health practitioner networks. Participants will be randomised to three individual sessions of either CCC or a standardised assessment condition (assessment as usual; AAU). The AAU assessment will include; a mental status examination, assessment of current disordered eating behaviours and cognitions, assessment of clinical history, and a physical examination. The CCC condition combines the AAU assessment components with shared collaborative formulation and tailored psychoeducation highlighting the consequences of the eating disorder on wellbeing and future goals in a supportive and motivating way.This intervention may provide an effective and feasible method of improving treatment engagement and outcomes for individuals suffering from AN, with the ultimate outcome of reducing the negative biopsychosocial impacts of this potentially severe and chronic disorder.