Root canal anatomy is highly complex and unpredictable. An awareness and thorough knowledge of internal and external root canal morphology contribute to the successful root canal treatment. Usually mandibular molars have two roots with three canals (Mesiobucccal, Mesiolingual & Distal). But in few teeth, the number of roots and canals vary. Mandibular molars can have an additional root located lingually (Radix Entomolaris) Or buccally (Radix Paramolaris). Clinicians should be aware of these unusual root morphologies in the mandibular first molar which needs strategic treatment as unfilled canals remain a nidus for infection and can compromise treatment outcome. This case series discusses endodontic treatment of Mandibular First Molar with Radix Entomolaris, which is a rare entity and poses as an endodontic dilemma for the clinician with respect to diagnosis and subsequent treatment.