Composite is a material made of two or more different materials with different properties in which they are not dissolving each other. Kenaf fibers reinforced polypropylene (PP) composite is used in automotive applications such as for set and door trim products. This research aims to produce the PP composite with three kinds of reinforcing materials: i.e. raw kenaf, alkalized kenaf and mixed kenaf and CaCO3 powder, and to compare the effect of alkalization and the addition of CaCO3 on the tensile properties of the composites. The kenaf/PP composites were fabricated using a hot press machine at 161-166C and 25-30 kg/cm3 with the fiber content of 30% (w/w) and a fiber length of 6 mm. Ten (10%) CaCO3 was also added into the kenaf/PP composite. Before composite fabrication, kenaf fibers were alkalized by soaking the fibers in 6% NaOH solution at room temperature for 4 h. CaCO3 powder used in this work was sieved with a 200 mesh sieve. The composite specimens were tensile tested and tensile test specimen was prepared according to ASTM D638-02. The tensile fracture surface was characterized by scanning electron microscopy (SEM). An optical microscope was used for characterizing the fiber distribution from cross-section view. The results showed that tensile properties are 46.82 MPa (tensile strength), 0.17 (tensile strain) and 458.77 MPa (tensile modulus) for raw kenaf/PP composite, 54.99 MPa (tensile strength), 0.18 (tensile strain) and 577.36 MPa (tensile modulus) for alkalized kenaf/PP composite and 42.46 MPa (tensile strength), 0.17 (tensile strain) and 424.74 MPa (tensile modulus) for CaCO3-kenaf/PP composite. Bonding strength between the fiber and the matrix and fiber distribution within the matrix due to alkalization is better than by the addition of CaCO3. These lead to be the higher tensile strength of alkalized kenaf/PP composite than that of CaCO3-kenaf/PP composite.