Calcifying Epithelial Odontogenic Tumor (CEOT), also known as Pindborg tumor, is a rare odontogenic benign tumor. It was first reported by Thoma and Goldman in 1946 and defined as an independent tumor by Pindborg in 1957. Herein, we reported a CEOT case involving most of the mandible after I-125 implantation in a 53-year-old man. We cooperated with governmental and hospital departments to resect the tumors, reconstruct the mandible with a fibular flap graft, and properly dispose of the radioactive particles.