Polymer nanocomposites are a field of numerous researches due to their improved properties compared to conventional polymeric materials and composites which enables them to be widely used. Nanofillers possesses remarkable properties because of their dimensions and structure which enabels them improve the properties of the nanocomosites. In this study the addition of carbon nanotubes (MWCNT) and modified carbon nanotubes (MWCNT-COOH) in the range of 0.5 wt. % to 5 wt. % in the polyamide matrix (PA) was investigated. PA and nanocomposite samples were prepared by melt mixing in a Brabender plasticoder and then pressed on a laboratory hydraulic press. For the purpose of analyzing the thermal, mechanical and electrical properties of PA/MWCNT and PA/MWCNT-COOH nanocomposites, the samples were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), THB thermal conductivity determination method, tensile test and electrochemical impedance spectroscopy (EIS). Results of DSC analysis showed that carbon nanotubes (MWCNTs) act as nucleation centers and accelerate the crystallization of PA matrix, but do not affect the order of the crystal structure. Due to the polar nature of the surface and the better dispersion, MWCNT-COOH fillers more significantly accelerate the PA crystallization compared to MWCNT. Although the carbon nanotubes have a nucleation effect, due to their presence the PA chains have limited motion space which interferes with the crystallization process of the matrix. The thermal stability of the PA matrix increases with the addition of both MWCNT and MWCNTCOOH fillers, and the start of decomposition moves to higher temperatures. The higher thermal conductivity is achieved by the addition of MWCNT-COOH filler compared to the addition of MWCNT. Such results are attributed to the good thermal conductivity of MWCNT. The results of the tensile test showed that by adding both types of MWCNT fillers in the PA matrix, the modulus of elasticity and the yield stress are reduced, but the yield strain increases. This behavior can be attributed to the effect of MWCNT fillers on PA which reduces the fraction of the matrix that can crystallize, which then affects the reduction of the modulus and yield strength and increases the deformability of the nanocomposite systems. The results of the EIS method of the electrical conductivity of the nanocomposites show equal impendance (resistance) as the pure PA matrix.