Biological functions of human cathelicidin LL-37 have been widely reported, including antibacterial, immune and anti-tumor effects. However, the antiplatelet activity of LL-37 has not been addressed. The purpose of our study was to investigate the antiplatelet and antithrombotic actions of LL-37. We found that this peptide inhibited human platelet aggregation in vitro and attenuated thrombus formation in vivo. Furthermore, LL-37 reduced phosphorylation of Src kinase and Akt(Ser473), decreased platelet spreading on immobilized fibrinogen and inhibited P-selectin expression on platelets. These results demonstrate that LL-37 has antiplatelet and antithrombotic actions. (C) 2016 Elsevier Inc. All rights reserved.