A patient with Frey syndrome on the left cheek area as a complication of an Obwegeser osteotomy is reported. Flushing, sweating of skin, and hypoesthesia of buccal mucosae were present 6 months after surgery. An injury to the auriculotemporal nerve during desperiostization of the posterior border of the mandibular ramus is believed to be the principal cause. The physiopathologic mechanism is thought to occur in relation to aberrant regeneration of the postganglionic secretomotor parasympathetic nerve fibers carried in this nerve. These regenerated fibers erroneously reach the sweat glands of the cheek skin through anastomosis with the buccal nerve and temporofacial ramus of the facial nerve. Direct injury of the buccal nerve may be another cause, because of its close anatomic course with the external pterygoid muscle and the mandibular ramus. An extensive literature review revealed no cases of this syndrome as a complication of Obwegeser osteotomy.