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Nickel catalysts supported on Ce_0.5Zr_0.5O₂, CeO₂/Al₂O₃, Ce_0.5Zr_0.5O₂/Al₂O₃, and Al₂O₃ were investigated for methane autothermal reforming. Samples were characterized by BET area, X-ray diffraction, H₂ temperature programmed reduction and temperature programmed desorption of CO₂. Nickel dispersion was evaluated using a model reaction, the dehydrogenation of cyclohexane. Light-off experiments showed that methane autothermal reforming occurred in two steps, by an indirect mechanism: total combustion at lower temperatures followed by methane reforming by CO₂ or steam at higher temperatures. Most catalysts exhibited good activity, stability, and a H₂/CO ratio around 2.7 during stability tests that lasted 24h. 10% Ni/Ce_0.5Zr_0.5O₂/Al₂O₃ showed the best activity and its performance could be explained by its higher reducibility and Ni dispersion.