Background/aim: This study was designed to develop a Behçet's disease (BD) symptom assessment scale based on the theory of unpleasant symptoms, which deals with understanding symptom experiences in a disease. Materials and methods: The BD Symptom Assessment Scale has two sections: the factors influencing symptoms and the situations influenced by symptoms. Both of these sections were developed through an initial item pool, and expert opinions were consulted during a pilot test performed with 30 patients with BD. We then tested the validity and reliability of this scale on 218 different patients with BD fulfilling the ISG criteria. Finally, we scored this scale. Results: The validity and reliability study of the first section found that the scale had favorable fit indices (X²= 525.86, X²/ SD = 3.15, GFI = 0.90, CFI = 0.89, IFI = 0.89), constituting three dimensions and 20 items. The validity and reliability study of the second section found that the scale had favorable fit indices (X² = 579.14, X² / SD = 3.48, GFI = 0.91, CFI = 0.89, IFI = 0.89) and constituted three dimensions and 20 items. Conclusion: This novel symptom assessment scale for BD is a valid and reliable tool for evaluating patients with BD.