Isothermal titration microcalorimetry experiments are performed to measure the heat of adsorption of poly(ethylene glycol) (PEG) on nonporous silica nanoparticles. A calorimetric technique is also developed for the determination of the adsorption isotherm for the PEG-silica system. A model based on the continuum form of the self-consistent field theory is used for estimating the polymer-surface interaction parameter, chi*, from the heat of adsorption of the polymer. The effect of temperature and molecular weight of PEG on chi* has been determined. It is shown that the adsorbed amount of PEG on silica, predicted using the estimated value of chi*, is in good agreement with the experimental data. We also find that the major contribution to the heat of adsorption arises from the bound fraction of the adsorbed polymer.