Plasma treatment methodology is widely used to functionalize the surfaces of nanofillers in order to enhance elastic, thermal and electrical properties of composites. In this study, plasma process of two types was employed for nitrogen doping on the surface of multiwalled carbon nanotube (MWCNT). First, nitrogen doping on MWCNTs was carried out in a horizontal quartz tube using N2 plasma at the powers of 100 W for 10 min. Second, MWCNTs were surface-modified with plasma treatments using nitrogen by nanocular instrument of 50mA for 1hr. The influence of the doping on the structure of CNTs was studied using XPS and Raman spectroscopy. N-doped MWCNT reinforced epoxy composites were fabricated and tested to investigate the effect of functionalized surfaces of MWCNTs. FE-SEM was used to confirm the dispersion and interphase of MWCNTs. In addition, quasi-static tensile tests were performed to examine the effect of various weight contents of MWCNTs, 0 to 1.0 wt%, on determining the bulk elastic composite properties.