The aim of this study is to investigate the influence of hybridization on lateral buckling behavior of composite beams consists of symmetrical and unsymmetrical ply orientations, various cutout shapes, and length/thickness ratio. Carbon, S-glass, and Aramid fibers are used as reinforcement with epoxy resin. Experiments are performed to see the effects of various combinations of fibers on lateral bucking loads with [(0/90) 3 ] s , [(30/-60) 3 ] s , [(45/-45) 3 ] s symmetrical, and [(0/90) 6 ] us unsymmetrical ply orientations. Numerical studies are also performed to see the effects of length/thickness ratio, and various cutout shapes on the lateral buckling loads using finite element analysis software ANSYS. It is concluded that stiffness and shear properties are affecting the lateral buckling characteristics of the composite beams. Also, fibers having higher stiffness and higher shear properties in the upper layers increase the lateral buckling strength. POLYM. COMPOS., 37:2511-2521