This case report describes mandibular reconstruction using a deep circumflex iliac artery (DCIA) flap, incorporating virtual surgical planning and 3D-printed surgical guides, following tumor resection. A 49-year-old male presented with an ulcerative lesion in the left posterior mandible. Following a diagnosis of squamous cell carcinoma (pT4aN2bM0), selective neck dissection (level I–IV) and segmental mandibulectomy were performed. Virtual surgical planning based on computed tomography images enabled the creation of patient-specific surgical guides. Reconstruction of the mandible and soft tissue was achieved using a DCIA flap that included the internal oblique muscle. The procedure lasted 605 minutes, with an ischemia time of 43 minutes. During a one-year follow-up, no complications or recurrences occurred, and functional and aesthetic outcomes were satisfactory. DCIA flap reconstruction with virtual surgical planning and custom surgical guides demonstrates effectiveness as a treatment for extensive mandibular defects.