Abstract Funding Acknowledgements Type of funding sources: None. Background While previous reports showed ADP-induced platelet reactivity to be an independent predictor of bleeding after PCI in stable patients, this has never been investigated in patients with cardiogenic shock (CS). Methods The association of bleeding events with respect to ADP-induced platelet aggregation was investigated in patients undergoing primary PCI for acute myocardial infarction complicated by cardiogenic shock (AMI-CS) and with available on-treatment ADP-induced platelet aggregation measurements. Results Out of 233 patients, 74 suffered from a severe BARC 3 or higher bleed. ADP-induced platelet aggregation was significantly lower in patients with BARC≥3 bleedings (10 AU [IQR 3 - 13] vs. 15 AU [IQR 9 - 25], p < 0.001). Multivariate analysis identified on-treatment ADP-induced platelet aggregation as an independent risk factor for bleeding (HR = 0.968 per AU, 95% confidence interval (CI) 0.942-0.994). An optimal cut-off value of <12 AU for ADP-induced platelet aggregation to predict BARC≥3 bleedings was identified via ROC analysis. Moreover, use of VA-ECMO (HR 1.972, 95% CI 1.003-3.879) or coaxial left ventricular pump (HR 2.593, 95% CI 1.509-4.455), first lactate (HR 1.093 per mmol/l, 95% CI 1.037-1.152) and thrombocyte count (HR 0.994 per G/l, 95% CI 0.990-0.998) were independent predictors of BARC≥3 bleedings. There was no significant difference in survival nor ischemic events between patients with low and high on-treatment platelet reactivity. Conclusion: Lower on-treatment ADP-induced platelet aggregation was independently associated with severe bleeding events in patients with AMI-CS. The value of platelet function testing for bleeding risk prediction and guidance of anti-thrombotic treatment in CS warrants further investigation.