In patients with severe carotid artery stenosis, the effects of carotid artery reopening, achieved either by carotid endarterectomy (CEA) or carotid artery stenting (CAS), on cognitive functions remain elusive. Herein, we conducted a prospective study to determine whether and to what extent CEA and CAS affected cognitive performance. Patients admitted to the Department of Neurology or Vascular Surgery in Nanjing First Hospital from December 2012 to March 2015 with a diagnosis of severe carotid artery stenosis (>70%) were included in the study. Among them, 77 patients underwent CEA, 81 patients underwent CAS, and 77 patients who refused to receive aforementioned interventions were enrolled in control group. Of note, all patients in this study received basic pharmacological treatment according to the American Heart Association/American Stroke Association guidelines. Cognitive functions were evaluated by a broad spectrum of neuropsychological tests including the Mini-mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA) and event related potential P300 on the day prior to and at 3 months after indicated intervention. When compared with basic pharmacological treatment, both CEA and CAS significantly increased the scores of MMSE and MoCA at 3 months following procedures. Meanwhile, a significant reduction of P300 score was also observed in patients underwent CEA or CAS. In addition, the changes in MMSE, MoCA and P300 scores over time between CEA and CAS groups were not statistically significant. Taken together, our findings suggest an improvement of cognitive functions following carotid artery reopening. Meanwhile, the beneficial effects of CEA and CAS on cognitive performance seem to be equivalent.