Cut-outs are often found in composite structures. These are provided with structural components for ventilation and sometimes to lighten the structure. This article addresses the effects of a cut-out on the buckling behavior of rectangular plates made of polymer matrix composites. While the loaded edges are modeled in simply supported boundary conditions, the unloaded edges are taken as free. Finite element analysis is also performed to predict the effects of cut-outs on the buckling behavior of these plates. Several key findings and behavioral characteristics are discussed. These findings include the effects of cut-out size, cut-out orientation, and corner fillet radius conditions.