This paper presents the findings of experimentally observed corrosion response of novel TiTaHf-based high entropy alloys (HEAs) in fetal bovine serum (FBS) to evaluate their biocompatibility in presence of proteins and potential to be used as implant materials. Particularly, TiTaHfNb, TiTaHfNbZr and TiTaHfMoZr HEAs were subjected to static immersion experiments in FBS media, and both the HEA samples and the immersion fluids underwent thorough characterization. The findings presented herein show that Zr and Mo addition to the TiTaHf solid solution increased the total ion release from the resulting HEAs in FBS, while the TiTaHfNb HEA became prominent in terms of biocompatibility owing to the reduced ion release in FBS. Moreover, hydroxy apatite (HA) formation was evident on the surfaces of all three HEAs upon immersion in FBS, indicating the potential of the three TiTaHf-based HEAs to form desired binding with the human bone. Considering the fact that passive oxide layer formation facilitating lower susceptibility to corrosion in long-term applications was also observed in the studied HEAs, further elaboration on their mechanical and biological responses is warranted for the sake of a comprehensive assessment regarding their utility as orthopedic implant materials.