Every tooth in the dentition can show very unique root anatomy along with variation in the number of canals in each root. The failure rate of nonsurgical root canal treatment is higher in the mandibular premolars due to difficulties in finding accessory canals explained in numerous studies. Clinicians should be aware and keep abreast with the complete assessment of the anatomy and morphology of the root canal system for a favorable treatment outcome. This case report illustrates root canal treatment for a rare case of a C-shaped with four root canals in the mandibular second premolar identified under a microscope and cone-beam computer tomography (CBCT) scan. This incidence has never been reported in the literature so far.