The Ni-Ce-O mixed oxide catalysts prepared by oxalate gel-coprecipitation were found to be highly efficient for the catalytic combustion of methane. Particularly, the relationship between the microstrain of NiO lattice due to the formation of CexNi1-O-x(y) solid solutions and the catalytic performance of Ni-Ce-O mixed oxides has been investigated as a function of the Ni/Ce ratio, showing that the lattice strain of the NiO crystals plays a significant role in the methane combustion reaction.