An experimental study was made to determine the characteristics of low-temperature creep in polycrystalline nickel during application and removal of a constant magnetic field of various intensities. It has been found that both application and removal of a magnetic field result in an increment of plastic strain in a ferromagnetic material. The dependence of softening effects on the magnetic field intensity and on the externally induced stress was another object of this study. Various possible mechanisms effecting the change of plasticity of ferromagnetic materials in a magnetic field are considered. The experimental results are theoretically analyzed on the basis of these concepts.