Background and Purpose-FABP4 (fatty acid-binding protein 4) is an intracellular lipid chaperone involved in coordination of lipid transportation and atherogenesis. This study aimed at observing the effect of FABP4 on the 3-month outcomes in Chinese patients with acute ischemic stroke.;-;Methods-In a prospective multicenter observational study, serum concentrations of FABP4 were on admission measured in plasma of 737 consecutive patients with acute ischemic stroke. Serum concentrations of FABP4, National Institutes of Health Stroke Scale score, and conventional risk factors were evaluated to determine their value to predict functional outcome and mortality within 3 months.;-;Results-During follow-up, an unfavorable functional outcome was found in 260 patients (35.3%), and 94 patients (12.8%) died. In multivariate models comparing the third and fourth quartiles to the first quartile of FABP4, the concentrations of FABP4 were associated with poor functional outcome and mortality. Compared with the reference category (Q1-Q3), the concentrations of FABP4 in Q4 had a relative risk of 4.77 (95% confidence interval [CI], 2.02-8.15; P<0.001) for poor functional outcome and mortality (odds ratio, 6.15; 95% CI, 3.43-12.68) after adjusting for other significant outcome predictors in univariate logistic regression analysis. Receiver-operating characteristic curves to predict poor functional outcome and mortality demonstrated areas under the curve of FABP4 of 0.78 (95% CI, 0.75-0.82) and 0.83 (95% CI, 0.79-0.88), which improved the prognostic accuracy of National Institutes of Health Stroke Scale score with combined areas under the curve of 0.83 (95% CI, 0.76-0.89; P<0.01) and 0.86 (95% CI, 0.81-0.92), respectively.;-;Conclusions-Data show that FABP4 is a novel independent prognostic marker improving the currently used risk stratification of stroke patients.