Introduction: The interplay between platelets and pro-thrombotic factors may have been under-investigated in the identification of aspirin users at high risk for cardiovascular event reoccurrences. There is growing evidence that a Prothrombin G20210A (FII) or a Factor V Leiden (FVL) mutation might increase platelet activity. Subsequently, this study assessed on-aspirin platelet (re-)activity in non-pregnant participants with a FII - or a FVL mutation in comparison with non-pregnant data derived from controls. Methods: This study was conducted with data derived from the follow-up FRUIT-RCT. This is a unique cohort namely, participants without a history of cardiovascular disease or thrombotic events, but who are a carrier of a pro-thrombotic mutation. All participants were instructed to ingest aspirin once daily for 10 days. Platelet (re-)activity was measured by the PFA Closure Time (PFA-CT), the VerifyNow (VN-ARU), and serum Thromboxane B2 (sTxB2) levels. Results: In total, eight participants with a FII-, 15 with a FVL mutation, and 21 controls were included. The FII mutation carriers demonstrated significantly higher on-aspirin platelet (re)-activity (PFA-CT, −92 sec.; VN-ARU, +37 ARU) vs. controls. The FVL carriers demonstrated similar on-aspirin platelet (re-)activity vs. controls. The sTxB 2 levels were similar in either of the carrier groups vs. controls. Conclusion: We feel these data are suggestive of increased on-aspirin platelet (re-)activity, as measured by the PFA-200 and the VerifyNow, in non-pregnant carriers of a FII-mutation, but not in carriers of FVL-mutation. Interestingly, this increased on-aspirin platelet (re-)activity is present in spite of low sTxB2 levels.