Abstract Body (Do not enter title and authors here): Recent studies suggest that prediabetes is not only a prelude to diabetes, but also is an independent risk factor for cardiovascular thrombotic events in young and aged people. However, the mechanisms that may promote platelet activation and thrombosis during prediabetes have not been studied. We hypothesized that in prediabetes, dysregulation of electron transfer and accumulation of mitochondrial oxidants promotes platelet activation and thrombosis, and that aging exacerbates the phenotype. We recruited young (18-50 year) and middle-aged (51-64 year) Veterans with prediabetes and age- and BMI- matched healthy Veterans. Compared to healthy cohort, platelets from prediabetes exhibited enhanced agonist induced platelet activation, mitochondrial oxidants, membrane potential and thrombus formation ex vivo in both young and middle-aged cohorts to a similar extent. Preincubation of platelets with either a mitochondria targetable superoxide dismutase (SOD) mimetic or MitoQ (transfers electrons from Complex I/II to complex III to lower superoxide generation within mitochondria), rescued the prothrombotic phenotype. We confirmed these platelet phenotypes in C57BL6/J mice fed high fat (HF) diet for 2 weeks (model of early diabetes). Importantly, HF-fed mice showed increased susceptibility to carotid artery and pulmonary thrombosis in vivo. Pharmacological treatment of HF-fed mice with SOD-mimetic or MitoQ, or genetic overexpression of catalase within mitochondria, rescued the prothrombotic state. This is the first report showing platelet hyperactivity and enhanced thrombotic susceptibility in prediabetes. Further, our findings suggest that enhanced mitochondrial oxidants due to the premature electron escape contribute to the phenotype. Our data imply a therapeutic potential of SOD-mimetic and MitoQ in lowering thrombotic burden in prediabetes.