Mandibular gingival squamous cell carcinoma (SCC) is the second most common oral cancer after tongue cancer. As these carcinomas often invade the mandible early, accurately defining the resection extent is important. This report highlights the use of preoperative virtual surgery data, computer-aided design and manufacturing (CAD/CAM) technology, surgical guidance, and extended reality (XR) support in achieving highly accurate marginal mandibulectomy without recurrence or metastasis. : CT imaging data obtained a month before surgery were imported into Materialize Mimics and Materialize Magics (Materialize, Leuven, Belgium, Ver22.0) CAD/CAM software and used to design an osteotomy guide. An STL file was generated, and the guide was fabricated using a 3D printer (Objet 260 Connex; Stratasys Ltd., Eden Prairie, MN, USA) prior to the operation. An XR application, installed on a HoloLens (Microsoft, WA, USA) head-mounted display, projected a hologram onto the surgical field. : The rapid intraoperative diagnostic tests were negative, and histopathology confirmed SCC without vascular or perineural invasion. No complications, including occlusal or feeding problems and sensory abnormalities, were observed. Postoperative imaging 3 years later showed no recurrence. : Combining CAD/CAM and XR techniques for mandibulectomy may improve surgical accuracy and safety in oral and maxillofacial surgeries, whereas in-house 3D printing aids in managing tumor progression.