Supported　WMoNi　diesel　ultra-deep　hydrodesulfurization　(HDS)　catalysts　with　enhanced　synergetic　effects　among　metal　species　were　prepared　with　W-　and　Mo-based　hybrid　inorganic–organic　nanocrystals　(HNCs)　as　the　W/Mo　precursors.　The　W-　and　Mo-based　HNCs　are　monodispersed　particles　with　similar　structure.　The　thus-obtained　supported　WMoNi　catalyst　has　superior　hydrogenation　and　direct　desulfurization　activities　for　dibenzothiophene　HDS　and　dramatically　higher　fluid　catalytic　cracking　diesel　HDS　performance　than　WMoNi/Al2O3　prepared　by　the　impregnation　method.　This　benefits　from　the　bimetallic　catalyst　precursor　WMo/Al2O3,　which　has　highly　dispersed　W　and　Mo　species　and　high　sulfidability　and　thus　generates　a　large　number　of　metal　sulfide　slabs　after　sulfidation.　The　highly　dispersed　W/Mo　sulfide　slabs　provide　abundant　edge　sites　for　dispersing　Ni　species,　facilitating　both　textural　and　chemical　synergisms　among　the　sulfide　phases　and　yielding　more　synergetic　NiWMoS　active　phases.　The　approach　opens　a　novel　route　to　optimizing　the　synergetic　effects　among　metal　species　in　supported　WMoNi　catalysts　for　diesel　ultra-deep　HDS.　©　2016　Elsevier　Inc.