Fabrication of E-glass/sisal/polypropylene (PP) hybrid composites with the fiber content of 30 % in volume fraction was carried out by sandwiching technique in a hot compression molding at 170C for around 15 min to study tensile properties of the hybrid composites and the important factors affecting the properties. Tensile properties of E-glass/sisal/PP hybrid composites, the surface morphology of sisal and E-glass fibers and tensile fracture and surface were examined using a universal tensile machine (SFL-20-350, Shimadzu) and scanning electron microscopy (SEM, TESCAN VEGA3 LMU), respectively. Alkali treatment of sisal fibers was carried out in the 6% NaOH at room temperature for 4 h to make better bonding strength between the fiber surface and PP matrix. The ratio of E-glass/sisal was varied; i.e. 10/20, 15/15 and 20/10 (volume fraction). Increasing the ratio of E-glass fiber/sisal fiber tends to decrease tensile strength, but increase tensile modulus of the Eglass/sisal/PP composites. The results showed relatively high tensile strength, although the contribution of E-glass fibers to sisal/PP composites was relatively small owing to weak interfacial bonding between glass fiber surface and PP matrix. The composite fabrication technique, the ratio of synthetic fiber and natural fiber, treatment condition for the fibers, and fiber length are suggested to be the main factors played in affecting tensile properties of the hybrid polymer composites