The　imperative　need　for　highly　active　bifunctional　electrocatalysts　accommodating　both　the　oxygen　evolution　reaction　(OER)　and　oxygen　reduction　reaction　(ORR)　has　intensified　for　the　development　of　advanced　rechargeable　Zn-air　batteries　(RAZBs).　Bifunctional　catalysts,　crucial　for　simplified　processes　and　enhanced　performances,　necessitate　additional　dimensions　to　host　a　greater　abundance　of　catalytic　sites　compared　to　their　monofunctional　counterparts.　Nanofiber　skeletons　with　multi-dimensional　nanostructure　building　blocks,　renowned　for　structural　tunability　and　high　porosity,　have　garnered　significant　interest　across　diverse　applications;　however,　their　synthesis　remains　a　formidable　challenge.　Herein,　we　present　an　innovative　synthesis　strategy　to　construct　nanofiber　electrocatalysts　with　three-dimensional　(3D)　hierarchical　building　blocks　(CoCNTs/PCNFs),　which　comprise　cobalt　nanoparticles　embedded　in　one-dimensional　carbon　nanotubes　growing　on　porous　carbon　nanofibers　that　expand　the　effective　number　of　OER　and　ORR　active　sites.　The　well-distributed　cobalt　nanoparticles,　coupled　with　the　large　specific　surface　area　and　high　conductivity　of　the　catalyst,　contribute　to　the　highly　desired　catalytic　properties　of　CoCNTs/PCNFs　toward　both　the　ORR　and　OER,　resulting　in　a　minimal　potential　gap　ΔE　of　0.71　V.　Assembled　Zn-air　batteries　(RZABs)　incorporating　the　CoCNTs/PCNFs　catalyst　demonstrate　a　high-power　density　of　262.6　mW　cm−2,　surpassing　the　performance　of　state-of-the-art　Pt/C　and　RuO2　catalysts.　This　work　introduces　a　promising　strategy　for　designing　bifunctional　oxygen　electrocatalysts,　opening　avenues　for　future　advancements　in　the　field.　©　2024　The　Royal　Society　of　Chemistry.