Although the use of nickel–cadmium batteries is decreasing mainly due to environmental concerns; nickel–cadmium batteries are the only ones that present an established recycling process. On the other hand, the fundamentals of such processes were not well studied. The aim of this work is to investigate the thermal behavior of the electrodes of nickel–cadmium batteries during the conditions used in the recycling process. Tests were carried out using a thermobalance simulating different recycling conditions. Vacuum decomposition of cadmium oxide occurs in two steps. The first step presents a fast rate of decomposition where almost 95% of the reaction is observed. The second step exhibits a low decomposition rate. The same behavior was observed using a reducing agent. Increasing the temperature increases dramatically the rate of cadmium oxide reduction and decomposition.