Transparent nanomaterial-based solar cool coatings (nSCCs) are composite materials made up of transparent thin-layered substrates incorporated with nanosized additives for the purpose of reducing solar heat gain and passive cooling in buildings. This review summarizes recent state-of-the-art development of transparent nSCCs from a nanomaterials perspective and their key applications in buildings. It is well known that solar heat gain into buildings through building envelopes is the dominant factor accounting for up to 60% of cooling loads, resulting in significantly high building energy consumption. Therefore, there is a strong interest in the research into nSCCs as a solar heat gain reduction and passive cooling method for building energy savings. To date, very few reviews have been reported for such nSCCs from the view of nanostructured materials; this review consequently seeks to highlight the roles of nanotechnology and nanomaterials in enhancing the performance of solar cool coatings. Since opaque cool coatings have been widely reviewed in the past and the related applications are limited to concrete walls and rooftops, only transparent clear nSCCs are discussed here, predominantly due to the fast gaining popularity of transparent glass facades and glazed building envelopes. Consequently, in this review transparent clear nSCCs are classified based on the types of nanosized additives and solar reduction mechanisms, followed by the discussion with respect to their synthesis techniques, morphologies, optical performance and their key building applications. This review would be useful for the scientific community and building industry to better understand the applications of nanomaterials in building and construction.