Aim: Platelet transfusion is an effective option to reverse platelet inhibition in thienopyridine-treated patients suffering from bleedings or requiring urgent surgery. However, in ticagrelor-treated patients, the previous studies revealed significant clinical effects to platelet rich plasma (PRP) but poor response to pooled platelets (PP) as used in clinical routine. The aim of this study was to elucidate a potential pathomechanism to explain the poor response of ticagrelor to PP. Methods and results: From 79 whole blood samples of patients treated with ticagrelor, prasugrel, or clopidogrel, the PRI-VASP was determined before and after in vitro platelet supplementation of PP or PRP at increasing concentrations. Compared to prasugrel- and clopidogrel-treated patients, the PRI-VASP of ticagrelor-treated patients showed no significant increase after in vitro administration of PP. PRI-VASP was performed in ticagrelor-treated samples after in vitro addition of 1: centrifuged PRP platelets resuspended in PP buffer, 2: PP with human serum, 3: human serum alone. Surprisingly, PP with human serum or human serum alone were able to significantly increase PRI-VASP in samples of ticagrelor-treated patients (11.7 ± 10.9 → 61.3 ± 10.9%, p = 0.006; 11.7 ± 10.9 → 54.1 ± 2.7%, p < 0.001). This effect could also be shown using human albumin (18.9 ± 5.1% → 80 g/l human albumin: 48.1 ± 8.3%, p < 0.001). Conclusion: The present study demonstrates that addition of human serum and human albumin alone is able to reverse the ticagrelor effects in vitro and supports our novel hypothesis of the importance of proteins in reversing the effects of ticagrelor by binding active ticagrelor.