Carbon nanotubes (CNTs) attract great interest in developing conducting polymer nanocomposites for various applications. This paper reported the preparation of CNT foam and corresponding nanocomposites using a monomer infusion process, aiming at eliminating the problems arising from the dispersion and possible re-agglomeration of nanofillers in a polymer matrix. Various techniques were employed to study the morphology and properties of the developed materials. The results showed that by using cotton as a template, CNTs were grown on the carbonized cotton fiber, forming foam-like hierarchical structures with excellent hydrophobic and absorption performance. The nanocomposites reinforced by CNT foam exhibited a satisfactory stability and reproducibility on piezoresistivity under the cyclic operations, and had the potential to be used as a sensor for measuring mechanical deformation in flexible electronics.