In this work, several novel techniques to fabricate nano-engineered polymeric composites (or nanocomposites) containing functionalized carbon nanofibers (CNFs) were developed. The methodologies address current manufacturing issues of nano-engineered polymeric composites by effectively incorporating functionalized CNFs into polymer matrix and glass fiber layers. For polymeric nanocomposites, optical images of the nanocomposites revealed uniform distribution and alignment of the CNFs in the direction of the electric field. Due to the similarity in the alignment morphology, it was observed that alignment structure of the functionalized CNFs was independent of the functional groups grafted to the CNFs. Test results indicated that mechanical and electrical properties (measured parallel to the direction of the aligned CNFs) of nanocomposites containing aligned CNF network were improved in comparison to nanocomposites containing randomly distributed CNFs and neat epoxy sample. Discussion regarding the contribution of CNF type towards the mechanical and electrical properties is presented. In the first hierarchical composites study, functionalized CNFs were uniformly incorporated into glass fiber layers without inducing significant CNF agglomerate through a simple filtration process. Both in-plane and out-of-plane electrical conductivity of hierarchical composites were comparable to the conductivity of carbon fiber composites due to the formation of conductive path by CNFs. The second study presented the synthesis of functionalized CNF/glass fiber assembly demonstrating that functionalized CNF entangled network can be used to join glass fiber layers in the absence of polymer matrix. Test results showed that the peeling force required to separate the functionalized CNF/glass fiber assembly was significant due to the functionalized CNF entangled network. Possible explanations for both studies are provided in order to investigate the contribution of functionalized CNFs in each form of material.