Probably, the biggest appealing materials in today’s digital world are nanocomposites (NCs), which have a place in practically every area of human lives. Polymer-based NCs remain the best popular, and these possess the maximum patrons among the many types of NCs. Polymers can be made in a variety of ways that are both simple and affordable. The remarkable features of polymer/SiO2 NCs motivated us all to concentrate our attention on them in the current chapter. This chapter focuses on the latest developments in the field of silica-based polymer nanocomposites. This chapter begins with an introduction of the fabrication strategies of silica nanoparticles, followed by the synthesis of silica-based polymer nanocomposites as well as their applications in various fields of life. In this chapter, synthesis techniques like in situ polymerization, melt-blending, solution mixing, and template synthesis are discussed. The most important method used for the preparation of silica-based polymer nanocomposites, the sol-gel technique, is also explained. Finally, future prospects and conclusion are provided.