Using all atom molecular dynamics and trajectory-extending kinetic Monte Carlo simulations, we study the influence of Al2O3 nanoparticles on the transport properties of ions in polymer electrolytes composed of poly(ethylene oxide) (PEO) melt solvated with LiBF4 salt. We observe that the mobility of Li+ cations and BF4- anions and the overall conductivity decrease upon addition of nanoparticles. Our results suggest that the nanoparticles slow the dynamics of polymer segments near their surfaces. Moreover, the preferential interactions of the ions with the nanoparticles are seen to lead to an enhancement of ion concentration near the particle surfaces and a further reduction in the polymer mobilities near the surface. Together, these effects are seen to increase the residence times of Li+ cations near the polymer backbone in the vicinity of the nanoparticles and reduce the overall mobility and conductivity of the electrolyte. Overall, our simulation results suggest that both the nanoparticle-induced changes in polymer dynamical properties and the interactions between the nanoparticles and ions influence the conductivity of the electrolyte. © 2015 American Chemical Society.