The mechanical properties of polypropylene/multi-walled carbon nanotube composite fibers were investigated. Polypropylene and multi-walled carbon nanotube were melt blended using a twin screw extruder and fibers were produced by a melt spinning apparatus with different draw ratios. Optical microscopy images from cross-section of the fibers showed agglomeration on carbon nanotubes in some parts of the matrix. The Young’s modulus and breaking stress of the drawn composite fibers with draw ratios of 4 were in the given order 2% and 3.6% higher than that of pure polypropylene fibers which were produced in similar conditions, respectively. With increasing the rotational speed of the screw in melt blending stage, the Young’s modulus and breaking stress and molecular orientation of the drawn composite fibers were increased. The obtained experimental results for Young’s modulus and yield stress of the composite fibers were compared with the amounts calculated from Halphin-Tsai, Krenchel and Pukanszky-Szazdi equations. The differences between the experimental and calculated results were probably due to the agglomeration of carbon nanotubes in the matrix and interaction of the polymer and carbon nanotubes.