Abstract: Transjugular intrahepatic portosystemic shunt (TIPS) implantation is an effective treatment of portal hypertension in patients with decompensated liver cirrhosis. However, some patients develop TIPS thrombosis with recurrence of portal hypertension. The role of platelets in TIPS thrombosis and the necessity of antiplatelet therapy is unclear. Therefore, we aimed to study platelet function in patients with liver cirrhosis prior to and after TIPS implantation. Platelet aggregation was tested in peripheral and portal-vein blood patient samples on the day (D) of TIPS implantation (D0), D4 and D30 following the procedure (platelet count above 100 × 103/μL, aspirin starting on D5) using whole-blood impedance aggregometry (WBIA) and light transmission aggregometry (LTA). In addition, surface platelet activation markers (P-selectin, activated GPIIb/IIIa) and platelet-neutrophil complexes (PNCs) were assessed by flow cytometry. Thrombin receptor activating peptide 6 (TRAP-6), adenosine diphosphate (ADP) and arachidonic acid (AA) were used as agonists. Healthy subjects were included as controls. Agonist-induced platelet aggregation was reduced (WBIA: TRAP-6 p