Behçet’s disease (BD) is a chronic systemic vasculitis distinguished by recurrent bouts of inflammation that affects numerous organs. In addition to a variety of mucocutaneous symptoms, notably recurrent painful ulcers in the mouth and genitals, there can be ocular, articular, vascular, gastrointestinal, cardiac, and neurological system involvement. Mucocutaneous manifestations are the defining characteristics of BD. The absence of a pathognomonic test requires the use of clinical criteria for diagnosing the disease, and mucocutaneous lesions, which figure often in the presentation and diagnosis, are considered the hallmark signs for diagnosis. Internationally accepted criteria for BD identify recurrent oral and genital ulcers, cutaneous lesions, and the skin pathergy reaction as key features due to their high sensitivity and/or specificity. The disease primarily presents with mucocutaneous lesions in most patients, often preceding the involvement of major organs and other disease symptoms. Hence, the timely identification of the disease’s mucocutaneous lesions is crucial for precise diagnosis, suitable treatment, regular monitoring, and prevention of major organ complications. Given that BD is characterized by recurrent oral and genital ulcers, the primary focus of the differential diagnosis is to identify other conditions that result in similar ulcers in these areas. Through a comprehensive medical history, examination, and laboratory tests, it is possible to rule out the diseases listed in the differential diagnosis and avoid misdiagnosis. This chapter aims to provide a thorough examination of the clinical spectrum of mucocutaneous manifestations and their differential diagnosis.