This study sought to assess and compare retrospective demographic and clinical data of oral lesions of lichen planus, pemphigus vulgaris, and mucous membrane pemphigoid from the records of the Department of Oral Pathology and Surgery, School of Dentistry, Universidade Federal de Minas Gerais, Brazil, covering a period of 55 years. Out of 25,435 specimens, these immunologically-mediated diseases accounted for 301 (1.18%) cases, of which 250 (0.98%) were lichen planus, 27 (0.11%) were pemphigus vulgaris, and 24 (0.09%) were mucous membrane pemphigoid. Lichen planus presented mainly as white asymptomatic plaques on buccal mucosa. Pemphigus vulgaris was usually characterized by multiple symptomatic erithematous ulcers on the buccal mucosa. Painful ulcers and/or blisters on the gingiva were the most common presentation for mucous membrane pemphigoid. Desquamative gingivitis was noted for all 3 diseases, but mainly for mucous membrane pemphigoid. Overall, lesions were more frequent in white women >50 years. Oral manifestations of immunologically-mediated diseases are relatively rare, and the correct diagnosis can be a challenge for dentists as the lesions often share similar clinical and demographic features.