Yttria　partially　stabilized　zirconia　was　introduced　into　WC-Co　cemented　carbides　to　enhance　their　mechanical　performance.　The　hardness　and　fracture　toughness　were　improved　simultaneously　with　the　addition　of　ZrO2.　Particularly,　the　fracture　toughness　of　the　cemented　carbides　was　significantly　enhanced.　The　mechanism　was　mainly　attributed　to　the　stress-induced　phase　transformation　of　tetragonal　ZrO2　to　monoclinic　ZrO2.　This　phase　transformation　introduced　a　compressive　stress　field　and　deflected　the　micro-cracks.　In　addition,　the　ZrO2　particles　dispersed　homogeneously　in　the　WC　skeleton　and　had　good　interfacial　bonding　with　both　WC　and　Co　phases,　which　was　beneficial　to　the　mechanical　properties　of　the　cemented　carbides.　This　study　provides　a　new　promising　approach　to　break　the　trade-off　between　the　hardness　and　fracture　toughness　of　cemented　carbides　to　achieve　excellent　comprehensive　mechanical　properties.　The　new　strategy　will　be　also　promising　to　be　applied　in　a　variety　of　cermets　or　ceramic-based　composites.　(C)　2021　The　Author(s).　Published　by　Elsevier　Ltd.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(http://creativecommons.org/licenses/by-nc-nd/4.0/).