Background: Accessory mental foramen (AMF) is the extra mental foramen (MF) located in the mandible. The recognition of AMF is important to avoid complications during surgical procedures involving MF and cheeks. Aim: This study aimed to determine the prevalence, localization, and size of AMF by using cone-beam computed tomography (CBCT). Materials and Methods: CBCT images of 645 patients over 13-14 years (male 281; female 364) were retrospectively evaluated. The CBCT images were obtained using Promax 3D (R) (Planmeca, Helsinki, Finland) device with automated exposure parameters varying depending on the cases. Statistical analysis was performed using descriptive statistics, chi-square test and t-test. Results: AMF was detected in 75 (11.6%) patients. There was no significant difference between the presence of AMF and gender (P = 0.57, P > 0.05). Majority of the cases (n = 67, 88.8%) consisted of single AMF, while double AMF was observed in 6 (10%) and triple AMF in 2 (1.2%) patients. The most common location of AMF with respect to MF was posterio-inferior (n = 57, 67.1%), and AMF placed at the root line of first molar tooth in 45 cases (52.9%). Conclusion: AMF can be seen in the mandible one in every ten patients being single in most cases. Considering the high prevalence and present morphological features, AMF should be detected by CBCT before surgical operations, particularly in implant planning for the prevention of possible complications.