We describe the simultaneous initial coexistence of mucous membrane pemphigoid (MMP) with blepharosynechia and anti-bullous pemphigoid (BP)180 antibodies and pemphigus vulgaris (PV) with lesions limited to the oral mucosa, with the presence of anti-desmoglein (Dsg)3 antibodies. A 75-year-old woman had severe oropharyngeal erosions and ulcers with blisters, and blepharoconjunctivitis and blepharosynechia of the left eye. Histopathological examination of the oral mucosa found acantholysis. Indirect immunofluorescence revealed IgG antikeratinocyte cell surface antibodies, and ELISA disclosed anti-Dsg3 antibodies. Immunoblotting found positive reactivity with recombinant proteins of both the BP180-NC16a domain and the BP180 C-terminal domain. To our knowledge, the simultaneous initial occurrence of MMP and PV has never been reported previously. We present a rare case of concurrent PV and anti-BP180 MMP, the diagnosis of which was confirmed by ELISA and immunoblotting assays.