Introduction: The root canal treatment of mandibular molars with aberrant canal configuration can be technically arduous requiring knowledge of anatomy, patience and perseverance. The present case report describes single sitting management in first mandibular molar having three mesial and two distal canals with new generation rotary file system. Neo Endo Flex Rotary File. Methods: Endodontic management of first mandibular molar with three mesial and two distal canals was done with Neo Endo Flex Rotary File system. Results: Patient was clinically asymptomatic and radiographically sound on follow up visits Conclusion: For successful endodontic treatment it is important to detect accessory and aberrant root canals and newer NITI file system can prove to be boon in managing such complicated canal architecture with great ease.