Gemination is a rare phenomenon in the maxillary posterior teeth. Endodontic treatment of these teeth requires special care due to the bizarre anatomy particularly when it is accompanied by a C-shaped canal system. This report illustrates a patient with a rare geminated C-shaped maxillary second molar comprised of two sections in its crown, including a geminated section attached to a normal coronal of a second maxillary molar diagnosed with the pulpal status "necrosis" and "irreversible pulpitis" in geminated section and the molar respectively. Thus, endodontic treatment was performed on both parts of the tooth. Two months follow-up revealed well-functioning teeth with normal status of periapical tissue with no mobility or abnormality. Successful treatment of unusual anatomical teeth requires adherence to biomechanical principles of canal preparation and coronal restoration.