Phononic　crystals　that　are　artificially　engineered　structures　have　recently　been　introduced　for　vibration　energy　harvesting　and　sensing　applications　due　to　their　unique　features　of　band　gaps　and　wave　propagation　control.　Conventional　energy　harvesters　made　of　phononic　crystals　are　mainly　designed　for　acoustic　energy　harvesting　at　a　high-frequency　vibration　source　(i.e.,　kHz　levels).　In　this　work,　a　defect-mode-induced　energy　harvester　is　designed　for　low-frequency　excitations　in　the　range　of　0–300　​Hz.　The　entire　system　that　is　a　locally　resonant　phononic　crystal　(LRPC)　plate　with　line　defect　patterns　is　consisted　of　elastic-wrapped　core　scatterers　periodically　embedded　in　epoxy　resin.　A　two-dimensional　(2D)　three-component　unit　cell　structure　is　arranged　on　the　plate　and　the　band　gap　property　is　analyzed　to　optimize　the　geometric　parameters.　Defects　are　then　introduced　to　the　LRPC　plate　with　a　7　​×　​7　point　array　for　analysis.　In　addition,　numerical　and　experimental　studies　are　conducted　to　investigate　the　performance　of　energy　harvesting　when　attaching　a　piezoelectric　patch　on　the　defect　points.　The　results　demonstrate　that　the　proposed　LRPC　vibration　energy　harvester　having　a　line　defect　mode　(with　continuous　or　alternate　points)　shows　good　performance　in　energy　harvesting,　in　which　a　peak　power　output　of　42.72　​mV　can　be　achieved　under　10　​m/s2　and　252　​Hz.　The　performance　is　almost　6　times　more　than　that　of　the　single-point　defect　model　under　the　same　excitation　conditions.　The　present　LRPC-type　energy　harvester　with　a　line　defect　mode　is　more　suitable　for　energy　harvesting　for　low-frequency　and　broadband　conditions.　©　2022　The　Author(s)