Purpose Most reports on the surgery-first approach in skeletal Class III malocclusion have focused on the skeletal changes. The present study evaluated the soft tissue changes around the lips over time after mandibular setback surgery (MS) with minimal orthodontics (MO) using 3-dimensional (3D) stereophotogrammetry. Materials and Methods We performed a retrospective study of patients with mandibular prognathism who had undergone MS-MO. Lateral cephalograms and 3D photographs were taken before (T0) and 1 (T1) and 6 months (T2) after surgery and were superimposed. A paired t test, independent t test, and simple linear regression analysis were used to evaluate the hard and soft tissue changes and their correlation. Results The sample included 15 patients (7 males and 8 females). The soft tissue landmarks on the X-axis (left-right) showed no significant positional changes. The landmarks of the lips and oral commissure on the Y-axis (vertical) moved downward until T2; however, most of these changes did not differ significantly over time (T1 compared with T0 and T2 compared with T0). The landmarks in the lower lip, oral commissure, and soft tissue chin on the Z-axis (anterior-posterior) showed posterior movement at T1 and T2. In contrast, the lower lip (labiale inferius, 1.67 mm) and soft tissue chin (soft tissue B point, 1.28 mm; soft tissue pogonion, 1.61 mm) moved significantly forward from T1 to T2, but had no correlation with the anterior relapse of the mandible. Conclusions Protrusion of the lower lip and soft tissue chin with forward and upward relapse of the mandible during postoperative orthodontics was observed. The results from the present study suggest that 3D stereophotogrammetry can be useful for evaluating the perioral soft tissue changes over time in orthognathic surgery patients.