Nanotechnology in construction and building materials has attracted great attention in recent years. Results demonstrated that nanomodification of cementitious materials can lead to significant improvement of the mechanical property, compactness, and durability. In this paper, based on the major characteristics of nanomaterials when used in cement-based materials, the recent progresses of nanomodification of cementitious materials with the mostly used nanomaterials such as nano-SiO2, nanoclay, nano-Al2O3, and carbon nano materials (carbon nanotubes and nanofibers) are reviewed. Modification effects and their influencing mechanisms of nanomaterials introduced by their specific features, such as the hydration seeding effect, the filling effect, the thixotropy-modifying effect, and the chemical reactivity feature on the properties of cementitious materials are reviewed. It is suggested that a stronger, greener, and more durable cementitious material can be obtained through the help of nanomodification.