Robust nanocoatings with both antireflective (AR) and antibacterial properties for transparent plastic substrates are not only significantly attractive in science but also urgently needed in wide applications. However, it is still a great challenge to realize the fabrication of this kind of multifunctional nanocoatings on plastic/polymer substrates. In this work, a series of single-particle-layered nanocoatings were prepared by partially embedding dendritic fibrous nanosilica (DFNS) with well-dispersed Ag nanoparticles (NPs) onto the surface of poly(methyl methacrylate) (PMMA) polymeric glass via organic vapor treatment. The optimal coated PMMA slide not only exhibits the enhanced transmittance with the highest one of 94.5% but also shows excellent antibacterial activity (at least killing 80% bacteria) toward both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Moreover, both long-term ultrasonic processing and pencil hardness tests proved strong adhesion of particles on PMMA substrate due to partial embedding. This work provides an exploration approach to construct the multifunctional nanocoatings on polymeric substrates for potential applications in various optical devices and daily touch plastic glass.