MicroRNA-210 (miR-210), a master and pleiotropic hypoxia-microRNA, plays multiple roles in brain ischemia. However, miR-210 expression and its function in humans have not been explored. The aim of our study is to evaluate the correlation of blood miR-210 with clinical findings in acute ischemic stroke. Blood samples were obtained from stroke patients (n=112) and healthy controls (n= 60). MiR-210 was measured at within 3, 7 and 14 days after stroke using a quantitative PCR technique. Stroke severity and clinical outcome were evaluated by NIHSS and modified Rankin Score. Both blood and brain miR-210 in ischemic mice was examined and the correlation was investigated. Compared to healthy controls, blood miRNA-210 was significantly decreased in stroke patients (0.93 vs. 1.36; P=0.001), especially at 7 days (0.56 vs. 1.36; P=0.001) and 14 days of stroke onset (0.50 vs. 1.36; P=0.001). The cut off point of miR-210 in diagnosis was 0.505 with 88.3 per cent sensitivity. MiR-210 level in stroke patients with good outcome was significantly higher than patients with poor outcome (1.2 vs. 0.44; P=0.012). The correlation between blood and brain miR-210 in ischemic mice was positive (R2=0.57, P=0.001). Blood miR-210 is a novel sensitive biomarker for clinical diagnosis and prognosis in acute cerebral ischemia.