Gut microbiota-derived bile acids are crucial in the pathogenesis and treatment of metabolic diseases. However, their impact on platelet activation and thrombosis in coronary artery disease (CAD) remains poorly understood. In this study, we observed reduced serum deoxycholic acid (DCA) in patients with CAD and an underrepresentation of Bacteroides vulgatus in the gut microbiota of patients with CAD, affecting DCA metabolism. We used Takeda G-protein-coupled receptor 5 (TGR5) inhibitors and TGR5 knockout mice to show that DCA inhibited agonist-induced platelet activation and thrombosis by interacting with the platelet TGR5. Oral gavage treatments with DCA, B. vulgatus and stool from healthy individuals suppressed platelet hyperreactivity and thrombosis in atherosclerotic ApoE mice, reduced microvascular thrombosis and protected the heart from myocardial ischemia/reperfusion injury. Here we describe the role of the bile acid DCA in platelet activation and suggest that targeting the gut microbiota and/or altering bile acid metabolism may be beneficial to treat CAD-associated thrombosis.