Endogenous and exogenous antioxidants have been shown to alleviate platelet activity, a known predictor of thrombotic states in cardiovascular diseases. Our hypothesis is that dietary polyphenols, rich in antioxidants, may possess anti-thrombotic potential and a possible natural complement to current antiplatelet therapy. Twenty-one healthy volunteers (M=10, F=11) participated in this randomized, double-blind, crossover trial. Volunteers consumed Queen-Garnet plum juice (QGPJ), prune juice (PJ) or control drink, 200 mL/day for 28 days. Blood and urine samples were collected before and after 28-days of supplementation. Full-blood examination and biochemical assays were performed before and after supplementation to evaluate the effect of polyphenols on cell counts, biochemical parameters, and inflammation markers. Platelet activity was evaluated using platelet aggregation assay, platelet surface-marker expression using flowcytometry and coagulation assays. Platelet aggregation was induced by exogenous platelet agonists such as ADP, collagen and arachidonic-acid. Platelet surface-marker expression was evaluated using PAC-1 (recognizes changes in GPIIb/IIIa complex of activated platelets) and P-selectin/CD62P (binds to activated-degranulated platelets) monoclonal-antibodies. Prothrombin time (PT), activated-partial thromboplastin time (APTT) and fibrinogen concentration was used to evaluate hemostatic function. Platelet aggregation induced by ADP, collagen and arachidonic-acid, was inhibited after QGPJ supplementation. Reduced P-selectin expression of degranulated platelets was observed post QGPJ supplementation. Prolonged activated-partial thromboplastin time was observed compared to the baseline. Fibrinogen concentration was alleviated post QGPJ. Cell counts, biochemical parameters, inflammation markers and PAC-1 expression did not change post treatment. Baseline values for all measurements remained unaffected post PJ treatment. The results indicate that active metabolites in QGPJ have the potential to attenuate platelet-activation and hyper-coagulability, hence require further investigation to study their effectiveness as possible antiplatelet therapy.