Background: This study aimed to identify and characterize root and canal morphology and the prevalence of C-shaped canals of mandibular second molars (MSMs) in a Yemeni population using cone-beam computed tomography (CBCT). Methods: CBCT images of 500 right and left MSMs with mature roots were taken from 250 Yemeni individuals and analyzed for the following features: number of roots, total number of canals orifices within the tooth and number of canals orifices in each root, type of roots, either fused or separated, shape of root in cross section, type of canal configuration in each root, presence of C-shaped canal, and primary variations in the morphology of root and canal systems. Results: Molars with separated two roots predominated (89.6%), fused two roots were 9%, separated three roots were 0.6% and one root MSMs were 0.8%. Molars with three canals orifices were the most common. Mesial root was mainly ribbon-shaped (60.5%) and distal root was mainly kidney-shaped (50.7%). Type II and Type I canal configurations were the most frequent in mesial root (56.9%) and distal root (91.3%), respectively. C-shaped canals were found in 9%. Six variants were found with variant 3 was the most common (71%). Conclusions: Yemeni permanent MSMs have mainly two separated roots. Mesial root is mostly ribbon-shaped and distal root is mainly kidney-shaped. Vertucci type II and I canal configurations showed the higher incidence in mesial and distal roots, respectively. C-shaped canals were found in 9%. Keywords: Cone-beam computed tomography, C-shaped canal, mandibular second molar, morphology, root canal, Yemen