Methods for inhibiting platelet aggregation using glucagon-like peptide-1 receptor (GLP-1R) agonists are disclosed. GLP-1 receptors are demonstrated to be expressed in platelets and/or megakaryocytes. Activation of GLP-1 receptors by GLP-1 agonists, such as GLP-1 and exendin-4, inhibited thrombin-induced platelet aggregation.