Objective To evaluate the reliability and effectiveness of a deep circumflex iliac artery based iliac-internal oblique musculofascial chimeric flap (DCIA-IIOF) in reconstruction of complex oromandibular defect. Methods Between January 2010 and December 2015, DCIA-IIOFs were used to repair complex oromandibular defects in 11 patients. There were 8 males and 3 females, with an age of 27-75 years (median, 56 years). Original disease was lower gingival squamous cell carcinoma in 7 cases (T3N1M0 in 2 cases, T3N2M0 in 1 case, T4N0M0 in 2 cases, and T4N2M0 in 2 cases), osteoradionecrosis after radiotherapy for nasopharyngeal carcinoma in 2 cases, central mandibular squamous cell carcinoma in 1 case (T4N0M0), and mandibular malignant fibrous histiocytoma in 1 case. The length of mandibular bone defects ranged from 7 to 10 cm (mean, 8 cm), and the area of the mucosal defects ranged from 5 cm×3 cm to 7 cm×4 cm. Preoperative ultrasonic identification of the DCIA and its ascending branch was routinely performed. The DCIA-IIOF was harvested by using an anterograde dissection technique, of which the iliac island was used for segmental mandibular defect repair and the musculofascial island for soft tissue and mucosal defect repair. Results All 11 cases were followed up 15-75 months (median, 37 months). All flaps survived after operation, without necrosis of both iliac island and oblique internal musculofascial island. One patient had a mild submandibular infection which healed after wound drainage and intravenous antibiotics. At 1 month after operation, the color and texture of the musculofascial island were similar to oral mucosa without contracture, and the occluding relation was good for all patients. At 6 months after operation, the mouth opening hardly improved in 2 patients who had osteoradionecrosis; 1 patient who underwent postoperative radiotherapy had restriction of mouth opening; the remaining 8 patients had normal month opening and normal diet. Three patients died of cancer recurrence, 2 patients died of other diseases (encephalorrhagia in 1 case and myocardial infarction in 1 case), and the others survived without recurrence during follow-up. No patient developed abdominal hernia during follow-up. Conclusion DCIA-IIOF is a reliable flap in reconstruction of complex oromandibular defects. The occluding relation after operation is good and the mucosal lining is soft. This technique provides an effective option for moderate complex oromandibular defects repair.