The purpose of this study attempted to analyze the potential risk factors for internal carotid artery injury during simple nasopharyngeal surgeries with or without an endoscopic aid. One hundred and seventy magnetic resonance imaging scans (340 halves) of the brain were retrospectively reviewed and studied. Anatomic variations of carotid arteries were classified, and various distances from the internal carotid arteries to the nasopharyngeal subsites were directly measured on the scans. The mean distances between the internal carotid arteries and nasopharyngeal subsites were significantly shortened in patients with nasopharyngeal internal carotid artery aberrancy, female gender, and lower body weight. The distance to the posterior nasopharyngeal wall was also shortened with age. However, the severity of nasopharyngeal carotid artery variations (kinking and coiling) did not reflect the shortening of mean distances to nasopharyngeal subsites. In conclusion, from multiple linear regression analysis, we found that the risk of an internal carotid artery injury during simple nasopharyngeal surgeries with or without an endoscopic aid is greatest in adult patients with nasopharyngeal carotid artery aberrancy, followed by female gender, lower body weight, and increasing age.