Ferric sulfate supported on zirconia catalysts were prepared by drying powdered Zr(OH)₄ with ferric sulfate aqueous solution followed by calcining in air at high temperature. The characterization of prepared catalysts was performed using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), and by the measurement of surface area. The addition of ferric sulfate to zirconia shifted the phase transition of ZrO₂ from amorphous to tetragonal to higher temperature due to the interaction between ferric sulfate and zirconia, and the specific surface area and acidity of catalysts increased in proportion to the ferric sulfate content up to 6 wt % of Fe. For samples below 6 wt % of Fe the decomposition of ferric sulfate supported on ZrO₂ occurred in one step, while for samples above 10 wt % of Fe the decomposition occurred in two steps due to the presence of two kinds of ferric sulfate, that is, ferric sulfate forming a monolayer and that exceeding the formation of complete monolayer on the surface of ZrO₂. On the basis of results of XRD, DSC, TGA, surface area, and acidity it is concluded that the content of ferric sulfate monolayer covering most of the available zirconia is estimated to be 6 wt % based on Fe. Infrared spectra of ammonia adsorbed on Fe₂(SO₄)₃/ZrO₂ showed the presence of Bro¨nsted and Lewis acid sites on the surface of Fe₂(SO₄)₃/ZrO₂.