Amine functionalized multiwalled carbon nanotubes (a-MWNT) based polypropylene (PP) composite fibers were prepared in the presence of polypropylene-g-maleic anhydride (PP-g-MA) by melt-mixing followed by melt-spinning with subsequent post-drawing of the as-spun fibers of varying draw ratio (DR). In order to enhance the interfacial interaction, a-MWNT were utilized in combination with PP-g-MA during melt-mixing. Fourier transform infrared spectroscopic analysis revealed the formation of imide bonds between MA functionality of PP-g-MA and amine functional group of a-MWNT. Higher tensile properties of PP/a-MWNT/PP-g-MA composite fibers were registered with varying DR of the as-spun fiber. Orientation factors of a-MWNT and PP chains along the fiber axis were correlated with the higher tensile modulus and tensile strength of PP/a-MWNT/PP-g-MA composite fiber of varying DR. Crystallization studies indicated the role of hetero-nucleating action of a-MWNT in PP/a-MWNT/PP-g-MA composite fiber. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers