This study examined how the diameter and length of corn husk fiber affects the mechanical, fatigue, and DMA properties of epoxy-based composite material. As filler, biosilica, which is made from wheat husks, was used to make composites. By hand layup process, the composites were created and then characterized as per the ASTM standards. Results revealed that the N21 composite designation offered improved tensile and flexural strength, Izod impact and hardness up to 94 MPa, 137 MPa, 3.62 J, and 86 shore-D. But compared to all composite designations, the composite designation N23 has the highest tensile and flexural strength, Izod impact, and hardness values, which are 134 MPa, 182 MPa, 4.84 J, and 88 Shore-D, respectively. Similarly, the composite designation N21 gives improved fatigue life counts of 21,629 by adding 1vol. % of biosilica and fiber length of 70 mm and diameter of 200 μm. In the same way, the highest storage modulus and loss factor of 5.5 GPa and 0.3 were noted for composite N23. The fiber diameter of 200 μm and a length of 70 mm demonstrate effective load shearing phenomenon and bonding between the fiber and matrix. Overall, the lesser diameter fiber with a higher length outperformed and it is recommended for high-performance composite making.