As a sustainable approach to reduce greenhouse gases emission during cement production and waste generation from steel manufacturing industry, ground granulated blast furnace slag (GGBFS) has been widely used as a cement replacement material for concrete production. However, due to its low pozzolanic activity, GGBFS causes delay in early strength development leading to prolonged curing of concrete. In this study, the influence of nanosilica (Ns), a highly reactive pozzolan on the properties of GGBFS concrete was examined. Different concrete samples containing intermixed GGBFS (0-30%) and Ns (0-3%) by weight were produced. The workability, setting time, compressive strength, tensile strength, water absorption and sorptivity of the samples were tested. The results show that the addition of nanosilica improves compressive strength and tensile strength of the GGBFS concrete. Therefore, the combination of GGBFS and Ns can be used for the production of good quality