Our aim was to assess the impact of combined orthodontic–surgical treatment on patients’ oral health-related quality of life (OHRQoL) according to type of dentofacial deformities, by synthesizing the available evidence. Methods: Search was conducted in the PubMed, Embase/MEDLINE, Scopus, and Cochrane databases. The eligibility criteria were studies that measured OHRQoL before–after orthognathic surgery, with results disaggregated by Class II and III. Two researchers independently performed the selection process, data extraction, and methodological quality assessment. Meta-analysis of the standard mean differences (SMD) was performed using random effect models. Results: The search identified 1047 references. Thirteen studies met the inclusion criteria, and four were included in the meta-analysis. The SMD of OHRQL global score showed large improvement 4–7 months after surgery in Class II and III patients (2.09, 95% CI 0.68 to 3.49 and 1.96, 95% CI 1.22 to 2.70, respectively). The sensitivity analyses, excluding studies with weak methodological quality, showed that Class III patients’ improvement in functional limitation was significantly higher than in Class II patients (SMD 0.57, 95% CI 0.12–1.02). Conclusions: There is not enough evidence to support differences between Class II and III patients in the OHRQoL impact after orthognathic surgery, but findings suggest lower improvement of some domains in Class II patients.