Mucous membrane pemphigoid is a rare autoimmune bullous disease characterized by involvement of oral mucous membranes in 90% of cases. A 49-year-old female patient presented with erosive gingival lesions with positive Nikolsky's sign, as well as vesicular lesions on the abdomen, forearms, and palmar regions, with 3 years of evolution. An incisional biopsy was performed and histopathologic examination of the oral mucous membranes revealed a lesion characterized by detachment of the lining epithelium, forming a subepithelial cleft. The lining epithelium presented areas of acanthosis, exocytosis, and spongiosis. In addition, a chronic inflammatory infiltrate was present in the adjacent connective tissue. The diagnosis was benign membrane pemphigoid. The patient was referred to an ophthalmologist for investigation of ocular involvement and treatment was carried out with oral corticosteroid of triamcinolone acetonide. Recognition of the oral lesions of pemphigus by the clinician, its early diagnosis, and prompt therapy are essential for a favorable prognosis.