Background: In patients with mild to moderate Parry-Romberg syndrome (PRS), plastic surgeons have mainly focused on the restoration of soft tissue deficiencies. While, bone deficits are easily overlooked. This study developed a new method combines the autologous mandibular outer cortex (MOC) grafting with fat grafting in mild to moderate patients with PRS, and apply computer-assisted techniques to improve the surgical outcomes and accuracy. Methods: Seven patients with mild to moderate PRS were prospectively enrolled in the study. Preoperative and 7 days and 6 months postoperative computed tomography (CT) and photographs were performed. Computer-aided design was done based on preoperative CT data. Surgical templates for MOC harvesting and grafting were designed and printed out. The topographic map of fat grafting was generated. The accuracy of MOC bone grafting was evaluated by the MOC thickness relative error, the MOC thickness accuracy at the preop most severe bone atrophy point (preop MSBAP), and the MOC volume accuracy. The percentage volume maintenance of the fat grafting surgery was assessed. Results: All 7 patients had ideal clinical outcomes with significant improvement in facial symmetry and no major complications happened. The average MOC thickness relative error is 2.85 +/- 0.50%. The average MOC thickness accuracy at the preop MSBAP is 3.36 +/- 1.13%. The average MOC volume accuracy is 3.41 +/- 1.37%. The average percentage volume maintenance of fat grafting is 62.79 +/- 5.73%. Conclusions: The combination of MOC grafting with fat grafting can be an excellent choice in reconstruction of mild to moderate patients with PRS. Applying computer-assisted techniques offers a reliable and accurate outcome.