Thermomagnetic measurements were used to determine the oxidation kinetics of bulk and powdered Nd‐Fe‐B magnets under a pressure of 1 Pa in the 360–600 °C temperature range. Those conditions are roughly similar to those undergone by sintered or rapidly quenched magnets during heat treatment. The first step of the oxidation kinetics obeys a parabolic law for bulk magnets and a cubic one for powders, with activation energies in the range 65–78 and 35–50 kJ/mol, respectively. Some anomalies in these patterns related to time or temperature are discussed.