INTRODUCTION One of the anatomical variant found in a permanent mandibular molar is Radix Entomolaris (RE) and was first described by Carabelli. It is an additional or extra third root. It is characterized by the presence of an additional or extra third root, which is typically found disto-lingually. When it is present bucally, it is called paramolaris. The success of a root canal treatment demands a proper knowledge and understanding of the unusual root canal morphology. This case report discusses the endodontic treatment of a mandibular molar with Radix Entomolaris.