Platelets are anucleated blood cells that play an important role both in the pathogenesis of atherosclerosis and subsequent thrombosis. Dendrimers have attracted great interest in biomedical applications. However, their interactions with cell compounds and compartments are nonselective, thus causing cytotoxicity and hemotoxicity. We derivatized PAMAM G4 and G5 dendrimers to evaluate their interactions with serum metabolites, their effects on the viability of red blood cells, and their antithrombotic properties. PAMAM G4 and G5 derivatives showed better hemocompatibility than the PAMAM G4 and G5 dendrimers without any derivatization (NH₂). PAMAM G4-Arginine-Tos and G4-Lysine-Cbz act as potent inhibitors of platelet aggregation induced by ADP. PAMAM G4-Arginine-Tos also showed inhibition of platelet aggregation induced by collagen, TRAP-6 and arachidonic acid. Moreover, G4-Arginine-Tos present inhibition of platelet secretion and thrombus formation under flow conditions. Based on our study, the PAMAM G4-Arginine-Tos derivative is hemocompatible and produces desirable antiplatelet and antithrombotic effects. Thus, this compound has potential applications as an antithrombotic drug or a drug delivery vehicle.