Dielectric barrier discharge (DBD) plasma was applied for the decomposition of nickel nitrate under air at ∼150 °C. Calcination (at 500 °C) under air and hydrogen reduction (at 500 °C) thermally were then conducted. The obtained Ni/SiO2 catalyst was investigated for steam reforming of methane (SRM) at the reaction temperatures of 600, 700 and 800 °C with a very low steam to methane molar ratio (H2O/CH4 = 0.5), in order to test the coke resistance of the catalyst. The DBD plasma prepared catalyst possesses an average particle size of 5.5 nm, much smaller than 15.3 nm of the thermally calcined one. The smaller catalyst size can lead to an enhanced coke resistance over the plasma prepared catalyst. The carbon nanotubes obtained on the used plasma prepared catalyst are very different from those formed on the calcined catalyst. The plasma decomposition is excellent for further investigation of effect of the catalyst structure beyond the nickel catalyst.