This study was carried out to compare the stability of Le Fort I maxillary advancement between the surgery-first approach (SFA) and the orthodontics-first approach (OFA), and to evaluate the impact of the quality of postoperative occlusion on maxillary stability. In total, 26 patients (13 SFA and 13 OFA) were included in this study. Cone beam computed tomography (CBCT) scans taken at T0 (1 week before surgery), T1 (1 week after surgery), and T2 (6 months after surgery) were used for the assessment of maxillary stability. The defective dentitions of the T0 and T1 scans were replaced with 3D-scanned dental models to assess the postoperative occlusions. The study was powered at 80%, with statistical significance for p <
0.05. No statistically significant differences in stability were found between the two groups. The mean posterior maxillary relapse was 0.68 ± 0.48 mm in the SFA group and 0.48 ± 0.38 mm in the OFA group. Quality of occlusal contact was poorly correlated with maxillary relapse in both groups. The stability of Le Fort I maxillary advancement was similar in the SFA and OFA patients at 6 months following surgery. This was independent of the quality of the immediate postoperative occlusion.