<p>Most oral malignant tumors are primary, and the incidence of oral metastatic tumors is low at 1%-2.4%. We report a rare case of mandibular metastatic lung cancer with multimodal imaging. A 67-year-old man presented with pain of the left side of mandible within 2 weeks. On clinical examination, swelling and redness of the gingiva of the left lower molar regions were found. Panoramic radiography revealed a mass like radiopacity on the left mandible, however, no destruction in the left mandible. CT showed metal artifact in the left mandible. On intraoral ultrasonography, the mass revealed clear boundary, hypoechoic echogenicity, homogeneous internal architecture, no vascular signals by color Doppler imaging and heterogeneous hard by strain elastography. Furthermore, MR imaging was performed. The lesion in the left mandible showed low-signal intensity and homogeneous enhancement on T1-weighted images. T2-weighted and STIR images showed high-signal intensity. diffusion-weighted MR imaging of the lesions revealed high-signal intensity, and the apparent diffusion coefficient values of the lesion was 1.08 × 10^− 3 mm²s^− 1. The radiological diagnosis in the mandibular lesion was malignant tumor. Histopathological diagnosis by incisional gingival biopsy was adenocarcinoma. Thereafter, ¹⁸F-fluorodeoxyglucose PET/CT was performed, and revealed focal hypermetabolic area in the left side of mandible and right upper lobe of lung. Histopathological diagnosis by biopsy of the right upper lobe of lung was adenocarcinoma. Therefore, this case was diagnosed as mandibular metastatic lung adenocarcinoma. This case suggests that multimodal imaging could be effective for diagnoses of oral metastatic tumor.</p>