The effects of bucky paper interleaves made from carbon nanofibers on interlaminar shear properties of carbon fiber reinforced composites (CFRPs) are studied. The study includes fabrication of bucky papers, resin impregnation by different techniques, i.e., soaking, hot-compression and vacuum filtration, followed by β-stage curing and the integration with carbon fiber prepregs to produce CFRP composites with bucky paper interleaves. The vacuum infiltration technique results in the best quality of polymer impregnation through bucky papers. Remarkable 31% and 104% improvements in interlaminar shear strength and mode-II shear interlaminar fracture toughness of the multiscale composites, respectively, are achieved with the incorporation of interleaves at failure-prone locations. The pertinent mechanisms responsible for the ameliorating effects of interleaves include improved interfacial adhesion and matrix shear strength for the interlaminar strengthening and crack-tip bridging and meandering for the toughening. The present technique can be used to incorporate carbon nanotubes (CNTs) or carbon nanofibers (CNFs) of high contents to strengthen/toughen at selective locations in FRP composites, which has not been possible previously because of the high viscosity caused by randomly-oriented CNTs/CNFs in a polymer resin.