Castleman's disease is a rare, benign lymphoproliferative disorder of unknown origin. Paraneoplastic pemphigus is a common association which presents as oral mucosal ulcerations. Abdominal and retroperitoneal Castleman's disease present either as a localized disease or as a systemic disease. We hereby present a 15-year-old male patient with oral mucosal lesions with localized vague right lower abdominal mass who was diagnosed to have Castleman's disease with paraneoplastic pemphigus which was surgically excised.