After thorough clinical, radiological and histopathological examination, Maxillofacial Surgeon Dr. S. M. Balaji diagnosed it as odontogenic keratocyst (OKC) involving the left side of the mandible. Dr. Balaji has planned to remove the entire cystic lesion along with the lining and reconstruct the same in a single surgery. Intraorally, mucoperiosteal flap was raised and the cystic lesion was exposed. Infected cyst along with the lining and involving bone was removed in toto. For reconstruction of the mandible, costal graft was harvested from the ribs and stainless steel reconstruction bone plate was used. The mucosal flap was approximated in layers.