In　light　of　the　rapid　development　of　intelligence　and　miniaturization　in　electronics,　the　growing　demand　for　sustainable　energy　sources　gives　rise　to　a　plethora　of　environmental/mechanical　energy　harvesters.　However,　the　fluctuating　nature　of　these　generated　energies　frequently　presents　a　challenge　to　their　immediate　usability.　Although　electrolytic　capacitors　can　smooth　fluctuating　energy,　lacking　miniaturization　and　flexibility　constrain　their　potential　applications.　Conversely,　electrochemical　capacitors　(ECs),　particularly　fiber-shaped　electrochemical　capacitors　(FSECs),　can　offer　superior　flexibility.　Nevertheless,　the　inherent　trade-off　between　ion　transport　and　charge　storage　in　fibrous　electrodes　poses　a　significant　obstacle　to　their　filtering　capability.　Here,　a　hierarchically　3D　fibrous　electrode　that　effectively　balances　ion　transport　and　charge　storage　through　its　unhindered　primary　framework　and　intertwined　secondary　frameworks　is　presented.　The　resulting　FSEC　exhibits　an　exceptional　specific　areal　capacitance　of　1.37　mF　cm−2　with　a　phase　angle　of　−82°　at　120 Hz,　surpassing　that　of　fiber-shaped　filter　capacitors　and　most　non-fibrous　filter　ECs　previously　reported.　Additionally,　the　FSEC　displays　excellent　flexibility　and　high-frequency　response,　rendering　it　well-suited　for　filtering　arbitrary　ripple　voltage　and　compatible　with　environmental/mechanical　energy　harvesters.　These　results　demonstrate　a　promising　approach　for　designing　fibrous　high-frequency　response　electrodes　and　a　foundation　for　portable　environmental　energy　harvesting　devices.　©　2023　Wiley-VCH　GmbH.