The response of the electrochemical quartz microbalance (EQCM) to the adsorption of t-butanol was measured. A positive frequency shift was obtained, similar to previous work on the adsorption of n-butanol and pyridine on gold. A detailed analysis of the effects contributing to the change in frequency was performed. For discussion of the shift in frequency caused by the changes of mass, the surface excess was measured independently. The importance of measuring activity coefficients of the electrolyte and the organic compound in order to obtain correct surface excess values is shown. Only a small frequency shift is expected due to the changes of mass on the surface. The residual frequency shift is attributed to changes in the properties of the interface. Since t-butanol molecules replace the water molecules, the ability to form bonds with further layers changes completely. The t-butanol is adsorbed on the surface through the hydroxyl group, with the methyl group facing the solution. The fact that the methyl groups of the t-butanol form fewer bonds is the main reason for the positive frequency shift observed.