The steam reforming reaction of methane to synthesis gas (CO and H2) was investigated in a very broad steam-to-carbon (S/C) ratio range (0.2–7.1) over a Ni/NiAl2O4 catalyst at 843, 858, and 873 K. The dataset includes 179 data points at each temperature giving a detailed insight in the gradual change of kinetic orders in both methane and steam with changing S/C ratios as well as with total reactant partial pressures at differential conversion levels. At low S/C ratios, steam dominates the kinetics with high kinetic orders (low for methane) and vice versa for methane at high S/C ratios. The extent of the water gas shift reaction was assessed by 13CO2 co-feed experiments and thermodynamic modelling and found to be not in equilibrium. A change in the kinetic isotope effect (i.e., inverse and normal), as well as the apparent activation energy, was observed depending on the applied S/C ratios. The experimental data were satisfactorily described by a Langmuir–Hinshelwood expression.