Shear stress (SS)-induced platelet activation is suggested as an essential mechanism of the acute coronary syndrome (ACS). We aimed to compare SS-induced thrombotic and thrombolytic activities among 3 treatment regimens in patients with ACS who underwent percutaneous coronary intervention (PCI). Patients were nonrandomly enrolled and treated with one of 3 regimens (TICA: ticagrelor 180 mg/d; RIVA: clopidogrel 75 mg/d and rivaroxaban 5 mg/d; CLP: clopidogrel 75 mg/d), administered in addition to aspirin (100 mg/d) for 30 days. The global thrombosis test was applied to measure SS-induced thrombotic (occlusion time [OT]) and thrombolytic activity (lysis time [LT]) at day 2 and 30. Aspirin reaction unit (ARU) and P2Y12 reaction unit (PRU) were simultaneously measured using VerifyNow. Group differences in the OT, LT, ARU, and PRU were evaluated. Seventy-five patients (25 patients in each group) finished 30 days of follow-up. Clinical and angiographic characteristics did not differ among the 3 groups, except ACS subtype and pre-PCI coronary flow. No major adverse cardiovascular events occurred in any group during follow-up. The OT and LT did not differ among the 3 groups at day 30 (OT: TICA, 447.2 ± 87.1 vs RIVA, 458.5 ± 70.3, vs CLP, 471.9 ± 90.7, LT: 1522.3 ± 426.5 vs 1734.6 ± 454.3 vs 1510.2 ± 593.9) despite significant differences in the PRU among the 3 groups. Shear stress–induced thrombotic and thrombolytic activities did not differ among the 3 investigated antithrombotic treatments.