Background: Cerebral endothelial cells (CECs) play a key role in mediating cerebral vascular hemostasis. The biological function of CECs in stroke patients remains unknown due to technical challenges to acquire patient CECs. We isolated and analyzed the function of CECs from living stroke patients. Methods: Cells were isolated from stent retrievers used for mechanical thrombectomy (MT) for patients with large vessel occlusion (LVO) after completion of the intervention as part of an IRB approved protocol. Patient endothelial cells (pCECs) were analyzed. Results: We isolated 300-400 primary brain endothelial cells per retriever from 5 patients with LVO with ages ranging from 69 to 86 years. The pCECs exhibited a typical monolayer cobblestone appearance and expressed VE-cadherin, but not α-smooth muscle actin, indicating that these cells are CECs. Western blot analysis showed that compared to human primary brain microvascular endothelial cells (hBMECs, Cell System), pCECs expressed significantly increased iNOS, VEGF, and VEGFR2, but reduced eNOS and Ang1. In vitro endothelial permeability and angiogenesis assays showed that pCECs robustly increased cell leakage and angiogenesis, respectively. Moreover, treatment of healthy hBMECs with exosomes derived from patient CECs (pCEC-Exos) significantly increased cell leakage and reduced cell integrity, which were associated with the reduction of tight junction proteins ZO1 and Occludin. Blockage of the caveolin endocytotic pathway by nystatin abolished the effect of pCEC-Exos on hBMEC function. Conclusions: Our data demonstrate that: 1) pCECs from stroke patients can be harvested; 2) pCECs are dysfunctional, and 3) pCEC-Exos induce dysfunction of healthy CECs. These data provide novel insights into the mediation of stroke-induced neurovascular dysfunction by pCECs.