Catalytic hydrogen combustion (CHC) is a promising technology for clean, efficient, and safe energy generation in hydrogen-fueled systems such as fuel cells and passive autocatalytic recombination. This study investigates catalytic hydrogen combustion over the Pd-Cu/Al2O3 catalysts at low temperatures (<125 °C) to determine the rate law using a differential fixed-bed reactor. The particle size distribution and reducibility of the catalysts were studied to investigate the influence of the catalyst composition on its reactivity. Higher reduction temperatures promoted the formation of metallic Pd, leading to improved catalytic reactivity at the optimized composition of Pd0.75Cu0.25/Al2O3. Furthermore, the rate law of CHC over the optimized catalyst was determined by non-linear regression based on the experimental reaction rates obtained under different partial pressures of H2 and O2. The Langmuir-Hinshelwood single-site mechanism was found to provide the best description of the catalytic combustion of hydrogen at low temperatures.