Tumour markers are used for the screening, diagnosis, and stratification of cancer disease. Recently, the potential role of some tumour markers has also been explored in the context of heart failure. These include CA-125, CA 15-3, CA 19-9, carcinoembryonic antigen, alpha-feto protein, tissue polypeptide antigen, tissue polypeptide specific antigen, cytokeratin 19 fragment, and chromogranins. Of these markers, CA-125, a tumour antigen that is expressed on the surface of ovarian cancer cells and which is a well-established biomarker for monitoring ovarian cancer growth, has been investigated most extensively. Trials have consistently indicated that CA-125 could serve as both a diagnostic and prognostic biomarker of heart failure, although the pathophysiology remains to be established. In this review paper we discuss the potential role of tumour markers in heart failure with a special focus on CA-125 within the context of recent trials.