Epicardial adipose tissue (EAT) is a metabolically active visceral fat depot closely linked to the pathogenesis of heart failure (HF). But the molecular signatures related to the mechanism of HF have not been systematically explored. Here, we present comprehensive proteomic analysis of EAT in HF patients and non-HF subjects as controls. A total of 771 proteins were identified in liquid chromatography-tandem mass spectrometry experiments. Among them, 17 increased in abundance in HF and 7 decreased. They were involved in HF-related processes including inflammation and oxidative stress response and lipid metabolism. Of these proteins, Serine proteinase inhibitor A3 (Serpina3) levels in EAT were highly upregulated in HF, with HF/non-HF ratio of 4.63 and a P value of 0.0047. Gene expression of Serpina3 via quantitative polymerase chain reaction was significantly increased in the HF group. ELISA analysis confirmed a significant increase in circulating plasma Serpina3 levels in the HF group (P = 0.004). In summary, for the first time we describe EAT proteome as a possible trigger for HF. Our profiling provides a comprehensive basis for linking EAT with pathogenesis of HF. Understanding the role of EAT may offer new insights into the treatment of HF.