Steam reforming (STR) and autothermal reforming (ATR) of n-heptane were studied on a 15 wt-% Ni/Al2O3 catalyst. The optimal temperature for H2 production is 700 °C, where both the conversion of n-heptane and the selectivity to H2 were high. At lower temperatures, thermal cracking of n-heptane occurred. The catalyst was active and selective, but coke accumulation was observed. Oxygen present in the ATR experiments reduced coke accumulation, which slowed the deactivation. According to the thermodynamics, the optimal O2/C ratio was 0.34 mol/mol at 700 °C.