Lip defects (including the corners of the mouth) are a reconstructive challenge in terms of both aesthetic and functional outcomes. When oral cancer resection results in defects that extend beyond the corners of the mouth to the buccal mucosa and buccal skin, it is difficult to perform reconstructive surgery using only a local flap, and a free flap must be used in combination. In this report, we present a case of reconstructive surgery of the corners of the mouth, buccal mucosa, and buccal skin after tumor resection for buccal mucosal squamous cell carcinoma in a 70-year-old man. The patient presented with a change in an oral in ticosal ulcer for a period of 1 year. After biopsy of the ulcerated area, he was pathologically diagnosed with squamous cell carcinoma. After tumor resection, including the corners of the mouth, lips, and cheek skin, and neck dissection, the patient underwent reconstructive surgery using an extended upper lip flap combined with an Estlander flap and a free anterolateral thigh flap. Two months after surgery, the patient was able to consume regular food. At 24 months of follow-up, the patient was able to speak normally without any restrictive symptoms such as fluid leakage from the corner of the mouth. Lip sensation restoration was optimal. This method using the combination of an anterolateral thigh flap and extended Estlander flap is a markedly useful option for reconstructive surgery of defects around the corner of the mouth caused by wide excision of invasive cancer.