Nanomaterials have an important role for enhancingthe concrete properties and inhibition of rebar corrosion in reinforced concrete. Nanosilica (NS) is one of the most effective cementitious materials, which possess high pozzolanic nature. In this work, NS was added in mix design of concrete with different ratios as; 0, 0.5, 1, 1.5, 2and 2.5 % by weight of Portland cement. Physical, mechanical properties (workability, density) were determinedfor the fresh concrete samples. While, compressive strength andmicrostructural properties of the interfacial transition zone (ITZ) between cement pastes and aggregates of concrete were investigatedfor the hardened samples.As well as electrochemical measurements (open circuit potential and linear polarization) were done for the reinforced concrete samples. The results show that, concretes containing NS up to 2% have a higher compressive strength and a denser in interfacial transition zone (ITZ). Also, corrosion inhibition for reinforced concrete increased gradually by increasing NS addition up to 2%.