|Introduction: The treatment of anorexia nervosa remains a matter of much debate. Though cognitive behavioural therapy would seem to offer good results, there is still no resounding evidence pointing to a single treatment of choice. The case presented in this paper examines the treatment with CBT of a patient presenting anorexia nervosa. Evaluation/diagnosis: An adolescent girl, 17 years of age, voluntarily attends psychological therapy to address eating behaviour problems. After administering the EAT-26, EDI-2, and BSQ standardised screening tests, as well as a clinical interview for assessment, a psychopathological profile is obtained, providing a diagnosis of anorexia nervosa, restricting subtype. Therapeutic goals: The therapeutic goals set were to reach a healthy weight for the patient’s age and height (specified as a minimum BMI of 18.5) and change the structure of thoughts, feelings, and behaviour that was justifying and maintaining the disorder. Treatment: Treatment lasted for 33 sessions and used cognitive behavioural techniques, such as cognitive restructuring, response cost, and positive reinforcement, in addition to family intervention techniques. Nutrition therapy was also carried out in parallel to the treatment sessions. Results: Following eight months of weekly sessions, the patient reached the target weight and changed attitudes towards food and body image, replacing them with healthy thoughts and behaviours. Follow-up made one and two years after the end of the treatment saw that these results were maintained. Discussion and conclusions: In this case, CBT proved effective in achieving the patient’s physical and psychological recovery. Therefore, this case contributes to the evidence of the efficacy of this therapeutic approach in certain cases of ED.