Mandibular gingival squamous cell carcinoma (GSCC) is a challenging malignancy often requiring extensive surgical resection and complex reconstruction. This study presents a 69-year-old male with left mandibular GSCC, treated with segmental mandibulectomy and selective neck dissection, followed by reconstruction using a deep circumflex iliac artery (DCIA) vascularized iliac crest flap with double musculocutaneous skin islands. Preoperative virtual surgical planning and 3D-printed surgical guides facilitated precise osteotomy and optimal flap design. The harvested iliac flap provided robust vascularization, adequate bone volume for mandibular continuity, and dual skin paddles for intraoral and extraoral soft tissue coverage. Postoperative evaluation demonstrated excellent functional and aesthetic outcomes, with stable osseous integration, viable soft tissue reconstruction, and no recurrence. This case underscores the versatility of the DCIA iliac crest flap in restoring both mandibular structure and oral function, highlighting advancements in microvascular surgery, 3D planning, and patient-specific reconstruction strategies. This case highlights the potential of the DCIA flap in addressing complex maxillofacial defects. However, it is critical to note that these findings are exclusively derived from a single-case analysis. Therefore, a larger cohort study is needed in future research to validate its applicability in practical scenarios.