Mandibular molars often exhibit variations in root morphology, one such variation is the presence of additional roots, the radix entomolaris (RE) or radix paramolaris. Understanding these anatomical variations is crucial for successful endodontic treatment outcomes. This report presents the endodontic treatment of a mandibular molar with RE, discussing its prevalence, external morphological variations, and internal anatomy. Key Messages: In this case report, we present a case of RE. Correct diagnosis of RE and understanding the RE's root inclination and root canal curvature is essential, as it requires a careful and tailored clinical approach to prevent or address procedural errors during endodontic therapy.