Key Clinical MessagesBehçet's disease (BD) or syndrome is a chronic, recurrent, multisystem, inflammatory vasculitis disorder with findings of oral aphthous ulcers, genital ulcers, and uveitis. Gastrointestinal (GI) involvement can be the initial presentation as presented in this case.AbstractBehçet's disease (BD) or syndrome is a chronic, recurrent, multisystem, inflammatory vasculitis disorder of unknown etiology with classical findings of oral aphthous ulcers, genital ulcers, and ocular involvements including chronic anterior, intermediate, posterior, and even panuveitis. Gastrointestinal involvement in BD usually presents with chronic diarrhea, hematochezia as the disease affects ileocecal area which might be similar to presentation of inflammatory bowel diseases. Here, we report a case of undiagnosed BD who presented with chronic diarrhea for 4 months, leading to the diagnosis of BD and responded well to corticosteroid therapy.