The microstructure of 44.7 Cu–20.6 Mn–34.7 Al (at.%) alloy, which exhibits a remarkable constricted hysteresis loop in the as‐cast state, has been investigated by transmission electron microscopy. It has been found that the constricted hysteresis loop is caused by the nonuniform precipitation of nonmagnetic Cu9Al4particles in the ferromagnetic Cu2MnAl matrix.