Oil Palm Empty Fruit Bunches (OPEFB) is an industrial waste of oil palm plantations which is increasing every year. The use of OPEFB fibers aims to utilize OPEFB waste to be more useful and economically valuable. OPEFB fibers are used as reinforcing materials/fillers for epoxy resin matrix. This study aims to determine the effect of the length of OPEFB fibers on the mechanical properties of composites being developed as an alternative material for plastic material substitution in the manufacture of helmet shells. The raw OPEFB fibers was boiled for 1 hour at boiling water. The volume ratio of fiber/matrix being used is 40:60, and fibers length variations are 5 mm, 10 mm and 15 mm. Specimens were fabrication using hand lay up and cold press technique with a pressure on the press gauge is 120 kg/cm2, with a holding time of 7-8 hours at room temperature. The mechanical tests performed are tensile and impact tests, according to the ASTM D 638-01 and ASTM D 6110 standards, Respectively microstructur fracture areas were characterized using an optical microscope. The results showed that specimens with 15 mm fiber length have the highest mechanical strength. Tensile strength 32.22 MPa, modulus of elasticity 2.61 GPa, and impact strength 32.10 kJ/m2, respectively OPEFB/epoxy composite is suitable to be used as an alternative material for manufacturing of helmet shells