This study describes an attempt to mechanically reinforce polypropylene (PP) using multi-wall carbon nanotubes (MWNTs) through a melt compounding process followed by hot-pressing and solid state drawing. The effect of a high density polyethylene (HDPE) coating on MWNTs and melt flow index (MFI) of PP on the dispersion of MWNTs and composite properties are studied by means of mechanical tests, transmission electron microscopy (TEM), scanning electron microscope (SEM), differential scanning calorimetry (DSC), and wide angle x-ray diffraction (WAXD). Highly orientated composite tapes are prepared to fully utilize the properties of MWNTs in uniaxial direction. Highly aligned MWNTs are shown by SEM, while highly oriented polymer chains are characterized by WAXD. Composite theory is used to analysis the results and indicates that effective reinforcement of PP by MWNTs is highest at relatively low filler content and draw ratios. (c) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 30-41, 2010