The effect of pressure up to 5.6 GPa on the magnetic behaviour of gamma '-Fe₄N has been investigated using the ⁵⁷Fe high-pressure Mossbauer effect technique at 300 K. We show that the decrease of the average magnetic hyperfine field at 300 K in this pressure range results from the decreases of the Fe local magnetic moment and Curie temperature with pressure. The decreases of the average isomer shift and the isomer shift for each Fe site with increasing pressure indicates a corresponding increase of s electron density at the ⁵⁷Fe nucleus, which is mainly caused by the volume compression of the 4s conduction electrons and changes of charge transfer between atoms.