For a successful root canal treatment, it is critical for the clinician to have a complete knowledge of the root canal morphology, interprets radiographs critically and properly assesses the pulp chamber floor. Anatomical variations are critical in diagnosis and a successful treatment outcome in endodontics. Knowledge of root canal morphology and anomalies is essential to succeed in root canal therapy. Mandibular premolars are famous for their atypical morphology. But the occurrence of type XVII Sert and Bayirli's root canal type is very rare in them. The purpose of this case report is to present treatment of a seldom root canal system in a mandibular second premolar. Reports of unusual cases cause clinicians to do an accurate clinical examination and radiographic interpretation and consider atypical root canal configurations.