The prognostic value of the N-amino terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP) in acute ischemic stroke (AIS) is uncertain. We sought to determine whether NT-proBNP levels were associated with functional outcomes after AIS. From August 2012 to October 2013, consecutive first-ever AIS patients admitted to the Department of Emergency of the First Affiliated Hospital of Xinxiang Medical University, China, were included in this study. Plasma NT-proBNP levels were measured from admission. Outcomes were measured as 90-day modified Rankin Scale score ('good outcome'=0-2 vs. 'poor'). Multivariate logistic regression was used to assess associations between NT-proBNP levels and outcomes. Predictive performance of NT-proBNP as compared with the clinical model was assessed by comparing receiver-operating characteristic curves. During this study period, 217 consecutive patients with AIS were included and completed 90 days of follow-up. There was a strong positive correlation between the plasma level of NT-proBNP and the National Institutes of Health Stroke Scale score (r=0.415, P=0.000). Plasma levels of NT-proBNP in patients with an unfavorable outcome were significantly higher than those in patients with a favorable outcome [3432 (interquartile range, 1100-54991) vs. 978 (interquartile range, 123-1705) pg/ml; P=0.000]. In multivariate analyses, after adjusting for all other significant outcome predictors, the NT-proBNP level that remained can be seen as an independent unfavorable outcome predictor, with an adjusted odds ratios of 4.14 (95% confidence interval, 2.72-7.99; P=0.000). Our results show that plasma NT-proBNP levels were significantly elevated in patients with an unfavorable outcome and might be of clinical importance as a supplementary tool for the assessment of functional outcomes in patients with AIS.