The　demand　for　electrochemical　sensors　with　high　sensitivity　and　reliability,　fast　response,　and　excellent　selectivity　has　stimulated　intensive　research　on　developing　highly　active　nanomaterials.　In　this　work,　freestanding　3D/Co3O4　thorn-like　and　wire-like　(nanowires)　nanostructures　are　directly　grown　on　a　flexible　carbon　fiber　paper　(CFP)　substrate　by　a　single-step　hydrothermal　process　without　using　surfactants　or　templates.　The　3D/Co3O4　thorn-like　nanostructures　show　higher　electrochemical　activity　than　wire-like　because　of　their　high　conductivity,　large　specific　surface　areas,　and　mesopores　on　their　surface.　The　characterization　of　3D/Co3O4　nanostructures　is　performed　by　using　high　resolution　transmission　electron　microscopy　(HRTEM),　field　emission　scanning　electron　microscopy　(FESEM),　X-ray　photoelectron　spectroscopy　(XPS),　X-ray　diffraction　analysis　(XRD),　and　electrochemical　methods.　The　3D/Co3O4　thorn-like　nanostructures　displayed　non-enzymatic　higher　catalytic　activity　towards　the　electrochemical　detection　of　glucose,　compared　to　the　3D/Co3O4　wire-like　morphology.　The　3D/Co3O4　thorn-like　nanostructures　show　a　wide　linear　range　response　of　glucose　concentration　ranging　from　1　to　1000　μM　with　a　detection　limit　of　0.046　μM　(S/N　=　3).　The　3D/Co3O4　thorn-like　nanostructure-modified　CFP　electrode　selectively　detects　glucose　in　the　presence　of　100-fold　excess　of　interfering　compounds.　The　3D/Co3O4　thorn-like　nanostructure-modified　CFP　electrode　is　tested　with　human　blood　serum　samples　and　validated　with　commercial　glucose　sensors.　The　newly　developed　sensor　material　shows　potential　for　glucose　monitoring　in　clinical　and　food　samples.　©　2017　The　Royal　Society　of　Chemistry.