Polymeric nanocomposites have attracted considerable interest, compared to traditional polymeric composites, because of their substantially improved mechanical, thermal, electrical, and magnetic properties, while maintaining their light-weight advantage. One of the most widely investigated and researched types of nanocomposites is carbon nanotube (CNT) reinforced polymeric resins, because of their promising property improvements, enhanced performance, and multifunctionality, which make them very attractive for high-performance structural applications. Carbon nanotubes can be synthesized in various geometrical shapes and configurations with different structural characteristics and material properties. Some of the main challenges for the effective incorporation of CNTs in polymeric resins are their agglomeration, non-uniform dispersion, and poor bonding/interface with the molecules of host polymeric resins. Several solutions have been proposed and applied to CNTs to overcome these challenges, but not all of them were fully successful. One of the most effective methods is to change the structure of the side walls of carbon nanotubes by means of chemical functionalization using strong acids. The main objectives of this research are to study the effects of various chemical functionalization methods, structural geometries of CNTs, and weight percentages (wt%) on the mechanical and thermal properties of CNTs reinforced polymeric nanocomposites. Two geometrical configurations of CNTs (e.g., straight and helical) were functionalized using different chemical functionalization methods. Then, different weight percentages of the functionalized CNTs were mixed within a polymeric resin system and used to fabricate nanocomposite specimens for further characterization and testing. All testing procedures followed the American Society for Testing and Materials (ASTM) standards.