Background: Most of the characteristic facial features of patients with unilateral macrostomia are attributed to the malformation of commissure muscles. This study aimed to evaluate a modified surgical treatment for such patients that focuses on both appearance and symmetry. Methods: Twenty-seven patients with macrostomia underwent surgery using the proposed method. Facial measurements were analyzed preoperatively, 1 week postoperatively, and during a long-term follow-up using statistical software. Results: The overall length ratio of the healthy and affected sides of the vermillion preoperatively, 1 week postoperatively, and during the long-term follow-up was 1:1.61, 1:1.01, and 1:1.00, respectively (all, p > 0.05). The overall angle between the pupil line and the commissure line was 9.90° preoperatively, 2.34° postoperatively, and 3.31° during the long-term follow-up. There was no statistically significant difference in the covering relation of the upper and lower lips between the affected and healthy sides postoperatively (p > 0.05). 3dMD Dynamic Surface Imaging System (3dMD, Atlanta, GA, USA) showed a symmetrical three-dimensional commissure structure during long-term follow-up measurements. Conclusions: The symmetry and appearance of patients with macrostomia commissure significantly improved following this modified surgical method.