In the present study, the role played by the reactants concentration on the nonlinear response of a Belousov-Zhabotinsky (BZ) system to the addition of a self-assembling non-ionic polymer, poly(ethylene glycol) (PEG), has been assessed. The oscillatory parameters are influenced to an extent that significantly depends on the concentration of both the polymer and the Belousov-Zhabotinsky components. The effects obtained were attributed to the reaction among some of the BZ key species and the backbone and the alcoholic functional groups of the polymer, both in its monomeric and aggregated forms.Support to the proposed perturbation mechanism has been provided by performing numerical simulations with the MBM model and by characterizing the physicochemical behavior of the PEG aqueous solution by means of viscosimetric and spectrofluorimetric measurements.