The inferior alveolar nerve block (IANB) procedure delivers anesthetics to the pterygomandibular space through which the lingual nerve (LN) and inferior alveolar nerve (IAN) travel. Injury to the LN has been reported more often than injury to the IAN. However, the number of anatomical studies of LN injury is limited. We aimed to establish evidence by investigating LN and IAN anatomy at the level of the mandibular foramen (MF). Forty-four sides from 22 Caucasian cadaveric heads (16 fresh-frozen and six formalin-fixed cadavers) were used in this study. The LN and IAN were laterally dissected, and the diameter and the distance between the two nerves were measured at the level of the MF. The mean diameters of the LN and IAN were 2.57 mm and 2.53 mm in fresh-frozen specimens and 2.97 mm and 2.93 mm in formalin-fixed specimens, respectively. The mean diameters of the LN and IAN in all the specimens were 2.65 mm and 2.64 mm. The distance between the posterior edge of the LN and anterior edge of the IAN at the level of the MF ranged from 1.62 to 8.36 mm with a mean of 5.33 ± 1.88 mm. These findings could elucidate the risk of LN injury during the IANB procedure.