The purpose of this study is to investigate and to evaluate the effect of CeO2 loading in the Ce-Al mixed oxide (CeO2-Al2O3) on physicochemical properties as well as the ultrahigh temperature water-gas shift (UHT-WGS) catalytic performance of Ni/x wt.%CeO2-Al2O3 (xCe-Al; x = 1, 3, 5, 7, and 10) catalysts. The Al2O3 (Al) and the xCe-Al supports were synthesized via the sol-gel method. The Ni/Al and Ni/xCe-Al catalysts were prepared by the incipient wetness impregnation method. The catalysts were characterized using XRD, the N-2 adsorption-desorption isotherms, H-2-TPD, H-2-TPR, TEM and TGA/DTA. The UHT-WGS catalytic performance of these catalysts were carried out in a packed-bed tubular reactor. The results reveal that adding CeO2 to the Al2O3 support for the Ni supported catalyst increased the surface area resulting in the enhancement of nickel dispersion and reducibility of the Ni/xCe-Al catalysts. However, under certain circumstances, bulk CeO2 can separate from the support to the catalyst surface and partially cover the Ni metal in the case of high CeO2 loading. Compared to other catalysts, the Ni/5Ce-Al catalyst illustrates the highest UHT-WGS catalytic activity (CO conversion > 75%) with the maintainability. This proposed composition provides the appropriate Ni-Ce-Al interaction that also suppresses the graphitic/filamentous carbon.