<p>Stabilizing effects of deviators on flexural and lateral-torsional buckling behaviors of pre-stressed simply-supported/cantilever beams due to initial tension are re-examined using an analytical approach. A flexural and lateral-torsional buckling formulation of mono-symmetric steel beams with discrete deviators at irregular intervals pre-stressed by a rectilinear cable is presented based on total potential energy. Also, some interesting properties on spatial buckling loads and their mode shapes of the pre-stressed beams such as determination of effective buckling length and laterally un-supported length, buckling loads of pre-stressed simply-supported/cantilever beams and difference of two buckling mode shapes by a rigid body rotation, are addressed in a general form and rigorously proved through mathematical process.</p>