Abstract: The binder phase performs critically on the comprehensive properties of cemented carbides, especially the hardness (HV) and fracture toughness (K_IC) relationship. There are strong motivations in both research community and industry for developing alternative binders to Co in cemented carbide system, due to the reasons such as price instability, property degeneration, and toxicity. Herein, six kinds of high entropy alloys (HEA) including CoCrFeNiMn, CoCrFeMnAl, CoCrFeNiAl, CoCrNiMnAl, CoFeNiMnAl, and CrFeNiMnAl were employed as the alternative binder for the preparation of WC–HEA cemented carbides through mechanical alloying and two-step spark plasma sintering. The impacts of HEA on the microstructures, mechanical properties, and thermal conductivity of WC–HEA hardmetals were determined and discussed. WC–HEA hardmetals exhibited both superior HV and K_IC to WC–metal or WC–intermetallic cemented carbides, indicating that HEA alloys were not only harder but also tougher in comparison with traditional metal or intermetallic binders. The HEA bonded hardmetals yielded thermal conductivities much lower than that of traditional WC–Co cemented carbide. The excellent HV–K_IC relationship of WC–HEA facilitated the potential engineering structural application of cemented carbides.