A series of experiments were carried out in a pressurized thermogravimetric analyzer to study the effects of H2S on the reactivity of ilmenite oxygen carrier under pressurized conditions. The total pressure was maintained at 0.4 MPa(a). Methane was used as fuel, and its partial pressure was varied from 0.08 to 0.119 MPa. The concentration of H2S varied from 2020 to 3030 ppm. The test temperature ranged from 1073 to 1173 K. The results showed that the reactivity of the ilmenite oxygen carrier improved with the presence of H2S, for both the reduction and the oxidation steps. Scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses were conducted to assess sulfur deposition on the reduced ilmenite samples. Thermodynamic analyses were performed to help interpret the test results. A kinetic model was developed on the basis of the experimental results. The model showed an activation energy for ilmenite reduction with H2S of similar to 79 kJ mol(-1) when H2S was present and 104 kJ mol(-1) for pure methane.