Practitioners need to know the normal and complex anatomy of the root canal system of individual teeth. Maxillary central incisors almost in all cases have one root and one root canal system. This case report describes a non-surgical endodontic treatment of a double-rooted maxillary central incisor using cone-beam computed tomography (CBCT). A fourteen-year-old male with spontaneous pain of the maxillary left incisor showed the presence of an extra root on the periapical radiograph. CBCT was used to assess the root canal details that lead to finding a narrow root in the mesial of the main root. Also, a periapical bone defect was detected. Nonsurgical treatment of tooth performed. At the 3-month follow-up, the tooth was functional and the lesion was healed. Therefore, practitioners should consider the presence of extra roots and canals during root canal treatment. CBCT imaging helps in detecting the exact location of the extra root.