Glucagon-like-peptide-1 receptor (GLP-1R) agonists are under development as new drugs to treat type 2 diabetes, liver disease, obesity and cardiovascular diseases. Some of these drugs are solely agonists of the GLP-1R. It turned out that their benefit could be improved when they also stimulated the glucagon receptor (GCGR) and/or the glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR). Stimulation of GLP-1R in cell cultures but also in neonatal atrial and/or ventricular cardiomyocytes and adult atrial cardiomyocytes raised the activity of adenylyl cyclase and thus augmented the 3',5'cyclic adenosine monophosphate (cAMP) levels. We discuss here the acute contractile effects of such agonists on isolated human atrial and ventricular cardiac preparations from failing and non-failing hearts. We address the receptors involved, GLP-1R expression in various cardiac regions of the human heart, single and multiple receptor agonists and the post-receptor signal transduction system of the GLP-1R in the human heart. Some of the new drugs addressed are still in the early phases of clinical development. We critically discuss the experimental and clinical data available and we also define research needs for experimental and clinical studies.