To evaluate the association between plasma levels of copeptin and 1-year mortality in a cohort of Chinese patients with acute ischemic stroke. We prospectively studied 275 patients with ischemic stroke who were admitted within 24 h after the onset of symptoms. Copeptin and NIH stroke scale (NIHSS) score were measured at the time of admission. The prognostic value of copeptin to predict mortality within 1 year was compared with the NIHSS score and other known outcome predictors. Nonsurvivors had significantly higher copeptin levels on admission compared with survivors (P<0.0001). Multivariate logistic regression analysis showed that elevated plasma levels of copeptin were an independent stroke mortality predictor, with an adjusted odds ratio of 4.48 [95% confidence interval (CI), 2.18-9.06]. The area under the receiver operating characteristic curve of copeptin was 0.882 (95% CI, 0.847-0.921) for stroke mortality, which yielded a sensitivity of 90.7% and a specificity of 84.5%. Copeptin improved the NIHSS score (area under the curve of the combined model, 0.94; 95% CI, 0.91-0.97; P=0.011). Elevated plasma copeptin levels at admission were an independent predictor of long-term mortality after ischemic stroke in a Chinese sample, suggesting that these alterations might play a role in the pathophysiology of stroke.