The electrospinning process with an applied electric field is used to extrude submicron fibers from polymeric solutions and has been recognized as a viable method for dispersing and aligning nanoparticles into a nanofibrous polymer matrix. In this study, electrospun nanofibers containing multi-walled carbon nanotubes (MWNTs) were used as a preform to fabricate MWNT reinforced polymer nanocomposites. The electrospun nanofibers were prepared by electrospinning a solution of polyamide 6 (PA6) and multiwalled carbon nanotubes (MWNTs). Raman spectroscopy, TGA, DSC, XRD, and TEM showed that the MWNTs were well dispersed and aligned in the electrospun nanofibers. The electrospun nanofibers in mat form were then consolidated into a solid composite by a thermal pressing. The initial modulus and tensile strength of the nanocomposites were improved by the reinforcement of the MWNTs. However, their breaking strain was lowered. This shortcoming was overcome by introducing a functional group onto the MWNTs through a surface treatment. Overall, the current method (modification of MWNTs, electrospinning, and thermal fabrication) can improve the tensile properties, including initial modulus, tensile strength and breaking strain, of PA6/MWNTs nanocomposites.