Transgranular　brittle　fracture　is　the　dominant　failure　mode　of　brittle　materials,　including　ceramics　and　ceramic　matrix　composites.　However,　strengthening　these　materials　without　sacrificing　their　toughness　has　been　a　big　challenge.　In　this　study,　an　innovative　approach　is　proposed　to　achieve　coordinated　strengthening　and　toughening　of　ceramics-based　composites　by　introducing　specific　ductile　coherent　nanoparticles　into　ceramic　grains.　As　an　example,　the　WC-Co　cemented　tungsten　carbides　were　used　to　demonstrate　how　this　brittle　material　can　achieve　ultrahigh　strength　without　losing　toughness　by　seeding　metallic　nanoparticles　inside　WC　grains.　The　mechanisms　for　inducing　the　formation　and　modulating　the　amount,　size,　and　distribution　of　such　nanophase　within　the　ceramic　grains　were　disclosed.　The　fraction　of　transgranular　ruptures　of　the　brittle　ceramic　phase　was　reduced　significantly　due　to　the　presence　of　the　ductile　coherent　in-grain　nanoparticles.　Both　the　strength　and　strain　limit　of　the　cemented　carbides　were　remarkably　increased　compared　to　their　counterparts　reported　in　the　literature.　The　coordinated　strengthening　and　toughening　strategy　proposed　in　this　work　is　applicable　to　a　broad　range　of　ceramics　and　ceramic　matrix　composites　to　obtain　superior　comprehensive　mechanical　properties.　©　2024　The　Royal　Society　of　Chemistry.