Tumor vasculature is critically dependent on platelet mediated hemostasis and disruption of the same can augment delivery of nano-formulation based chemotherapeutic agents which depend on enhanced permeability and retention for tumor penetration. Here, we evaluated the role of Clopidogrel, a well-known inhibitor of platelet aggregation, in potentiating the tumor cytotoxicity of cisplatin nano-formulation in a murine breast cancer model. In vivo studies in murine syngeneic 4T1 breast cancer model showed a significant greater penetration of macromolecular fluorescent nanoparticles after clopidogrel pretreatment. Compared to self-assembling cisplatin nanoparticles (SACNs), combination therapy with clopidogrel and SACN was associated with a 4 fold greater delivery of cisplatin to tumor tissue and a greater reduction in tumor growth as well as higher survival rate. Clopidogrel enhances therapeutic efficiency of novel cisplatin based nano-formulations agents by increasing tumor drug delivery and can be used as a potential targeting agent for novel nano-formulation based chemotherapeutics.