We report on polymer light-emitting diodes (PLEDs) with embedded SiO2 nanoparticle interlayers. We fabricated PLEDs with a rather thick (180 nm) SiO2 interlayer between the hole injection layer and a 50-nm thin emission layer. We also made devices, where the interlayer was embedded inside the emission layer. The devices were characterized by electroluminescence and photoluminescence measurements and compared to the respective reference devices. We achieved an enhancement factor of 1.74 for the luminous efficacy and 2.13 for the current efficiency at 4000 cd/m2 for the PLED with the interlayer between the hole injection layer and the emission layer compared to the reference device. For PLEDs with the interlayer between the two emission layers, we obtained an enhancement factor of 1.68 for the luminous efficacy and 1.45 for the current efficiency at 4000 cd/m2 compared to the corresponding reference device. This surprising enhancement can be explained by a superposition of increased internal quantum efficiency and an increase in the extraction efficiency.