We aimed to investigate the relationship between platelet microRNA (miR-223 and miR-96) expression and clopidogrel responsiveness in patients with coronary heart disease (CHD).A total of 33 consecutive non-diabetic CHD patients scheduled for percutaneous coronary intervention were enrolled. Platelet reactivity after clopidogrel loading dose (300 mg) was determined by two methods [platelet reactivity index (PRI), measured by vasodilator-stimulated phosphoprotein (VASP) phosphorylation flow cytometry and ADP-induced platelet aggregation (PAG), measured by light transmission aggregometry]. Total platelet RNA was isolated from purified platelets (CD45 magnetic bead negative selection) to quantify miR-223 and miR-96 expression by real-time PCR.All subjects were dichotomized according to PRI medians (normal-responders: PRI 56.5%, n = 16) and PAG medians (normal-responders: PAG 43%, n = 16). Compared with PRI-determined normal-responders, miR-223 expression, but not miR-96, was significantly decreased in low-responders (P = 0.037). No differential expression of miR-223 and miR-96 was observed via PAG determination between normal- and low-responders. In addition, miR-223 expression, but not miR96, was statistically correlated with PRI (Spearman r = -0.403, P = 0.020). Stepwise binary logistic regression analysis revealed that among factors that potentially influence platelet reactivity (CYP2C19*2 loss-of-function genotypes, use of calcium channel blockers/proton-pump inhibitors, age, obesity, smoking and platelet microRNAs), decreased miR-223 expression was the only independent predictor associated with the presence of PRI-determined low responders to clopidogrel (OR 0.189, 95% CI 0.043 to 0.836, P = 0.028).The present work identifies decreased platelet miR-223 expression as a novel mechanism involved in blunted platelet response to clopidogrel in a Chinese population.