Kenaf (Hibiscus Cannabinus) natural fiber as reinforcing material (filler) has been developed to produce material for automotive applications, especially in manufacturing of car interior panels. The advantage of kenaf fiber are cheap and has relatively higher mechanical strength than other natural fibers such as hemp, coconut and sisal fibers. Natural fiber reinforced have mechanical strenght that still tends to be lower compared to synthetic fiber reinforced composites, so it is necessary to add another filler so that the mechanical strength increases. One of them is the addition of microsilica particles, also known as silica fume. In this research, untreated kenaf fiber with the length of 6 mm was used. The matrix and fiber volume ratio was 73:25%. The addition of silica fume particle size of 0.1-150 μm, 74 μm, and 37 μm equals 2% of different. Composite fabrication using the single layer randomly oriented fiber and using cold press molding machine with a measured pressure of 8 MPa at room temperature for 24 hours. The mechanical testings performed is a tensile test according to the ASTM D638-01 standard and a water absorption test according to the ASTM D570-98 standard with 48 hours immersion time. The fracture results of the tensile test were characterized using scanning electron microscopy (SEM) to determine the microstructure and macro photographs using an optical microscope to determine the distribution of fibers in the composite. The results showed that the addition of 2% silica fume increased the tensile strength of kenaf/epoxy composites. Kenaf/epoxy composites with the addition of 37 μm silica fume particles have the highest tensile strength and the lowest water absorption than those of 74 μm and 0.1-150 μm. The tensile strength and modulus of the specimen with 37 μm silica fume are 64.1 MPa and 6.6 GPa, respectively the thickness swelling is 5.72-7.23% and weight gain is 4.97- 8.28% within 12-48 hours.