A variety of natural fibers have been on research over the past years to develop alternative echo friendly materials that have comparable performance as their synthetic counter parts for use in composite materials. In this study, two different forms of date palm tree fibers were used as reinforcement materials to develop composite materials with polypropylene (PP) matrix. These two different date palm fibers are namely Date palm fiber (DPF) & Date Palm twigs (DPT). These fibers were surface modified using alkali treatment. Two different Percentages of PP (50%, 75%) were mixed with the each type of fibers to form composite pellets using double screw extruder. The mechanical properties of the different fibers reinforced composite, in treated and untreated condition were investigated. The effect of different weight fraction of Polypropylene matrix reinforced DPF or Twigs fiber composite was investigated. The results indicate that untreated DPF-PP composites possess better mechanical properties compared to all untreated & treated DPT-PP composites. Mechanical interlocking between untreated fibers and the matrix showed some increase in the mechanical properties of the untreated DPF-PP compared to the treated one. In both cases, composites having 75% PP has better mechanical properties than the 50%PP composites. This is due to the lack of compatibility between the fibers and the matrix.