The conformations of polymer chains in poly(ethylene oxide)/silica nanoparticles, PEO/SiO2, nanohybrids have been investigated through a combined approach that involves molecular dynamics (MD) simulations and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) measurements. Systems with different polymer molecular weights,nanoparticle radii, and concentrations have been employed to investigate the effect of the confinement on polymer conformations across a variety of different conditions. Qualitatively similar behavior between experimental and simulation results is observed since in both cases an increase of gauche population for the OCCO angle is attained, in comparison to the respective of the bulk. This increase becomes larger as the degree of confinement becomes higher. More specifically, both simulations and experiments indicate a corresponding progressive increase with the degree of confinement. On the contrary, the conformations of the C-O bond (COCC angle) seem to remain unaffected by the confinement, at least in the range of degrees of confinement covered computationally. In addition, chain dimensions in the nanocomposite are found to be slightly decreased compared to bulk, especially at low temperatures. This results in a reduced effective confinement that allows the polymer matrix to accommodate larger nanoparticle fractions.