Abstract: This paper is concerned with the plane waves in a magneto-thermo-viscoelastie initially stressed medium. Firstly, the basic equations of motion to be satisfied by the electromagnetic, displacement and temperature fields of a magneto-thermo-viseoe-lastic medium under initial stress have been deduced. They are then employed to investigate the propagation of plane waves in a magnetothermo-viscoelastic medium under two cases of initial stress: a) hydrostatic compression or tension; b) uniaxial compression or extension, and then the influence of weak coupling on the propagation of waves of the thermal and magnetic effect was studied. The results obtained are in complete agreement with the corresponding classical visco-elastic problems when the initial stress, thermal and magnetic couplings are absent.