Heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF) are distinct clinical entities, yet there is scant evidence for associations of proteomic signatures with future development of HFpEF versus HFrEF. We evaluated the association of 71 protein biomarkers with incident HFpEF versus HFrEF (left ventricular ejection fraction ≥ versus <50%) among Framingham Heart Study participants using multivariable Cox models. Among 7038 participants (mean age 49 years; 54% women), 5 biomarkers were associated with increased risk of incident HFpEF (false discovery rate q<0.05): NT-proBNP (N-terminal pro-B-type natriuretic peptide; hazard ratio HR, 2.13; 95% CI, 1.52-2.99; <0.001), growth differentiation factor-15 (HR, 1.67; 95% CI, 1.32-2.12; <0.001), adrenomedullin (HR, 1.58; 95% CI, 1.23-2.04; <0.001), uncarboxylated matrix Gla protein (HR, 1.55; 95% CI 1.23-1.95; <0.001), and C-reactive protein (HR, 1.46; 95% CI, 1.17-1.83; =0.001). Fourteen biomarkers were associated with incident HFrEF (multivariable <0.001, q<0.05 for all). Of these, 3 biomarkers were associated with both HF subtypes (NT-proBNP, growth differentiation factor-15, and C-reactive protein). When compared directly, myeloperoxidase, resistin, and paraoxanase-1 were more strongly associated with HFrEF than HFpEF. We identified 5 protein biomarkers of new-onset HFpEF representing pathways of inflammation, cardiac stress, and vascular stiffness, which partly overlapped with HFrEF. We found 14 biomarkers associated with new-onset HFrEF, with some distinct associations including myeloperoxidase, resistin, and paraoxanase-1. Taken together, these findings provide insights into similarities and differences in the development of HF subtypes. URL: https://clinicaltrials.gov/ct2/show/NCT00005121; Unique identifier: NCT0005121.