For BSA and β-lactoglobulin adsorption to hydrophobic interaction chromatography (HIC) stationary phases leads to conformational changes. In order to study the enthalpy (ΔH ads ), entropy (ΔS ads ), free energy (ΔG ads ) and heat capacity (Δc p,ads ) changes associated with adsorption we evaluated chromatographic data by the non-linear van’t Hoff model. Additionally, we performed isothermal titration calorimetry (ITC) experiments. van’t Hoff analysis revealed that a temperature raise from 278 to 308K increasingly favoured adsorption seen by a decrease of ΔG ads from −12.9 to −20.5kJ/mol for BSA and from −6.6 to −13.2kJ/mol for β-lactoglobulin. Δc p,ads values were positive at 1.2m (NH 4 ) 2 SO 4 and negative at 0.7m (NH 4 ) 2 SO 4 . Positive Δc p,ads values imply hydration of apolar groups and protein unfolding. These results further corroborate conformational changes upon adsorption and their dependence on mobile phase (NH 4 ) 2 SO 4 concentration. ITC measurements showed that ΔH ads is dependent on surface coverage already at very low loadings. Discrepancies between ΔH ads determined by van’t Hoff analysis and ITC were observed. We explain this with protein conformational changes upon adsorption which are not accounted for by van’t Hoff analysis.