<p>Enhancing the early strength of concrete is crucial for concrete construction in low-temperature environments and the production of precast concrete. However, traditional early strength agents and measures have various drawbacks. Due to the high efficacy of nano-C–S–H seeds in cement-based materials and its excellent designable molecular structure, interest in nano-C–S–H seeds has been growing. Therefore, this paper aims to comprehensively review the application of nano C–S–H seeds in cement-based materials, providing an effective way for readers to understand its performance. This paper details the preparation processes of nano-C–S–H seeds, as well as the micro–macro properties of cement-based materials incorporating nano C–S–H seeds. The results show that nano C–S–H seeds exhibited good nucleation and filling effects. The type of precursor materials also influenced the Ca/Si ratio and microstructure of nano C–S–H seeds. Optimizing the substitution rate of nano C–S–H seeds can produce cement-based materials with excellent micro–macro properties. Additionally, the incorporation of nano C–S–H seeds in cement-based materials significantly reduces energy consumption, offering good environmental benefits.</p>