Measurement of plasma concentrations of the biomarker copeptin may help identify patients with heart failure at high and low risk of mortality, although the value of copeptin measurement in elderly patients is not fully known. To evaluate the association between plasma concentrations of copeptin, a surrogate marker of vasopressin, combined with concentrations of the N-terminal fragment of the precursor to B-type natriuretic peptide (NT-proBNP), and mortality in a cohort of elderly patients with symptoms of heart failure. Primary health care population in Sweden enrolling 470 elderly patients with heart failure symptoms between January and December 1996. Clinical examination, echocardiography, and measurement of peptide concentrations were performed, with follow-up through December 2009. All-cause mortality and cardiovascular mortality. After a median follow-up of 13 years, there were 226 deaths from all causes, including 146 deaths from cardiovascular causes. Increased concentration of copeptin was associated with increased risk of all-cause mortality (fourth quartile vs first quartile: 69.5% vs 38.5%, respectively; hazard ratio [HR], 2.04 [95% confidence interval {CI}, 1.38-3.02]) and cardiovascular mortality (fourth quartile vs first quartile: 46.6% vs 26.5%; HR, 1.94 [95% CI, 1.20-3.13]). The combination of elevated NT-proBNP concentrations and elevated copeptin concentrations also was associated with increased risk of all-cause mortality (copeptin fourth quartile: HR, 1.63 [95% CI, 1.08-2.47]; P = .01; NT-proBNP fourth quartile: HR, 3.17 [95% CI, 2.02-4.98]; P < .001). Using the 2 biomarkers simultaneously in the evaluation of cardiovascular mortality, there was a significant association for copeptin in the presence of NT-proBNP (log likelihood trend test, P = .048) and a significant association for NT-proBNP (fourth quartile: HR, 4.68 [95% CI 2.63-8.34]; P < .001). Among elderly patients with symptoms of heart failure, elevated concentrations of copeptin and the combination of elevated concentrations of copeptin and NT-proBNP were associated with increased risk of all-cause mortality.