Patients with complex and severe eating disorders often receive a number of ineffective or/and insufficient treatments. Direct referral of these patients to highly specialized tertiary treatment facilities in an earlier stage of the disorder is likely to be more (cost)‐effective. The aim of the study was to develop a decision tool that aids clinicians in early identification of these patients. After identification of criteria that were indicative of severity and complexity of eating disorder psychopathology by means of a systematic review of literature and consultation of a focus group, a Delphi method was applied to obtain consensus from experts on the list of relevant criteria. Finally, the decision tool was validated in clinical practice, and cut‐off criteria were established. The tool demonstrated good feasibility and validity to identify patients for highly specialized tertiary care. The final decision tool consisted of five criteria that can easily be implemented in clinical practice. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association.