In this chapter, the method of producing a multiwalled carbon nanotube (MWCNT)-doped Polypropylene (PP) fine fibers via melt-blowing was demonstrated. The MWCNT-doped fiber mats were then applied as an interleaving veil to create hierarchical single-PP composites. The morphological, thermal and mechanical properties of the nanocomposite fibers are discussed. The effect of the nanocomposite fine fiber mat interleaving on the thermal and mechanical properties of the SPCs was systematically and comparatively investigated. Results implied that incorporating MWCNT increased the melt-blowing grade PP resin viscosity. Incorporating MWCNT enhanced the melt-blown (MB) PP fiber mat's specific strength by 78% and improved thermal stability. Hierarchical single-polypropylene composites (SPCs) were produced by film-stacking, for which a PP film was used as a matrix, a PP woven fabric was used as primary reinforcement, and the MB fiber mat was used as interleaves. Interleaving enhanced the SPC's tensile modulus by up to 37%. Interleaving of the MWCNT doped PP fiber mat provided a robust interfacial adhesion and higher damage tolerance under tensile load. Master curves were constructed from dynamic mechanical analysis (DMA) frequency sweep tests based on the time–temperature-superposition (TTS) principle. Results revealed that the SPCs storage modulus increased by 33%, while the tanδ decreased by around 10% with the interleaving PP/MWCNT fiber mat.