In this article, we creatively incorporated Ag–SiO₂ core–shell nanoparticles (Ag–SiO₂-NPs) into photo-/electro-active layers consisting of poly(3-hexylthiophene) (P3HT) and phenyl-C₆₁-butyric acid methyl ester (PCBM) in polymer solar cells (PSCs). By this way, the photovoltaic performances of PSCs have largely been enhanced. The results demonstrate a 13.50% enhancement of short-circuit photocurrent density (J_sc) and a 15.11% enhancement of power conversion efficiency (PCE) as the weight percent of doped Ag–SiO₂-NPs is 1.5 wt% in the active layer of corresponding PSCs. We attribute the enhancement to the localized surface plasmon resonance (LSPR) effect of Ag–SiO₂-NPs, by which the incident light harvesting is enlarged. Whereas, the incorporated bare Ag nanoparticles (Ag-NPs) in the active layer of PSCs decreases the PCE, which is ascribed to the quenching of excitons at the surface of Ag-NPs and the poor dispersion of Ag-NPs in the active layer. Importantly, this work provides a new approach to enhance the performance of PSCs via the LSPR effect of Ag–SiO₂-NPs other than via non-circular nanometals.