Microstomia is caused by congenital growth abnormalities, exposure to electricity or chemicals, or direct burns. In the case of burn-induced microstomia, treatment is difficult because of fibrosis at the burn site. During dental treatment, buccal retraction is necessary to access the posterior teeth. When performing maxillary sinus augmentation using the lateral approach, sufficient buccal retraction through the buccal vestibule is required. Implant placement with sinus augmentation in patients with burn-induced microstomia caused by is very difficult to treat. Herein, we describe the successful results of simultaneous bilateral sinus augmentation and implant placement along with commissuroplasty and upper-lip reconstruction using mucosal advancement in a patient with burn-induced microstomia.