In the current work, a modified method of friction stir process (FSP) based on ultrasonic vibration and modified FSP tool design was developed to disperse multi-walled carbon nano-tube (MWCNT) throughout nylon 6 matrix. To this end, Field emission scanning electron microscopy, X-ray diffraction, Vickers’ micro-hardness, and visual inspection were used to evaluate the fabricated nano-composites. Also, a modified design of FSP tool together with ultrasonic vibration were used to improve the impact and efficiency of FSP. Several experiments were conducted to approach an optimum range of FSP parameters (rotational speed and traverse speed). The scanning electron microscopy observations and X-ray diffraction patterns (XRD) declare that MWCNT was dispersed homogeneously throughout nylon 6 matrix. Micro-hardness results illustrate that homogeneous dispersion of MWCNT throughout nylon 6 matrix results in 33% increase of micro-hardness. In general, the obtained results declare that ultrasonic vibration causes an increase in traverse speed and production speed of nano-composite without affecting the homogeneous dispersion and hardness of nano-particles throughout the matrix. Also, it is clear that ultrasonic vibrations did not noticeably affect superficial form of nano-composites due to low traverse speeds used in ultrasonic assisted friction stir process.