This paper examines the significance of nano silica and micro silica mixture on the shear strength of reinforced concrete beams. The nano and micro silica mixture was used as a partial replacement for Portland cement. The shear strength of reinforced concrete beams with and without shear reinforcement is examined. Moreover, the influence of the multi-sized silica mixture was on other mechanical characteristics of concrete related to the shear behavior of concrete beams was also examined. The mixture of 2% nano silica with 8% micro silica mixture was found to lead to the highest compressive strength. The shear strength of the concrete beam incorporating 8% micro silica and 2% nano silica mixture was also improved. The significance of nano-micro silica on the concrete contribution to the shear strength of reinforced concrete beams is examined.