OBJECTIVE This study investigated the effect of temporomandibular disorders on quality of life (QOL) of patients with dentofacial deformities. STUDY DESIGN A case-control study was performed involving 3 age- and gender-matched groups: 38 preoperative participants, 38 postoperative participants, and 39 control participants. Temporomandibular joints were assessed using the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD axis I), and QOL was assessed using the Orthognathic Quality of Life Questionnaire (OQLQ) and the Short-Form Health Survey (SF-36). RESULTS Significantly lower OQLQ scores were found in postoperative patients with one or more RDC/TMD findings; the domains in which these occurred were mental health, dentofacial esthetics, and awareness of dentofacial esthetics for patients with myofascial pain; social aspects and awareness of dentofacial esthetics for patients with disk displacement with reduction; and all domains for patients with arthritis (all P < .05). CONCLUSIONS Despite the variable effect of orthognathic treatment on TMDs, the presence of TMDs in patients after treatment can have a negative effect on their QOL.