Low self-esteem is a common feature in Anorexia Nervosa (AN) and has been hypothesised to act as a predisposing, precipitating, and perpetuating factor. The aim of this study was to assess the effectiveness of a Cognitive Behavioural Therapy (CBT)-based self-esteem group in a naturalistic setting of patients with AN in an inpatient treatment programme. Included in this study were 119 female patients diagnosed with AN, with all participants completing self-report questionnaires before and after the intervention. The group consisted of five to six weekly sessions. The self-esteem group led to a statistically significant improvement in self-esteem, which could not be explained by an increase in BMI alone, suggesting that the group is facilitating positive changes within an AN group. The group also had a small effect on improving patients self-perceived ability to change. These findings suggest that the brief self-esteem group has some benefits in improving patients' self-esteem/self-efficacy and should be replicated in the future with a control condition to confirm findings.