Background: The external carotid artery (ECA) supplies blood to various facial and neck regions and may contribute to collateral cerebral perfusion. With the rise in carotid artery stenting (CAS) as a treatment for carotid stenosis, ECA overstenting has become a common procedure feature. This study aimed to assess the incidence, characteristics, and duration of facial pain following CAS, hypothesizing that ECA overstenting may contribute to facial pain. Materials and Methods: This prospective study included 55 patients treated with CAS for internal carotid artery (ICA) stenosis at a single center. Patients’ facial pain was evaluated using a numeric rating scale (NRS) before, immediately after, and 24 h post-CAS. Patient data, including demographics, comorbidities, and procedural details, were analyzed to assess the relationship between ICA stenosis degree, ECA diameter changes, and facial pain incidence. Results: CAS was associated with intraoperative facial pain in 27.27% of patients, with 7.28% reporting residual pain 24 h post-procedure. Pain occurrence was significantly higher in patients with lower ICA stenosis (p = 0.04). The median ECA diameter decreased from 4.11 mm to 3.16 mm (p < 0.001) after CAS, with ECA overstenting observed in 96.4% of cases. No significant relationship was found between pain severity and stent width or length. Conclusions: This study highlights that CAS significantly decreases the diameter of ECA. Additionally, ECA overstenting might be associated with perioperative and postoperative facial pain, emphasizing the need for careful monitoring of ECA patency following CAS.