Buckling of simply supported rectangular sandwich plate with multi-blade stiffeners is addressed herein. The main objective was to present and validate an approximate, semi-analytical computational model for such plates subjected to in-plane loading. The faceplates are modeled as shear-deformable plates using first-order Shear Deformation Plate Theory (SDPT). The core of the sandwich panel is treated as three-dimensional body. The stiffeners were added at the upper faceplates and modeled as simple beams with flexural stiffness only against out-of-plane bending. Nonlinear finite element analysis was used to verify the accuracy of the presented model. The results of the presented model are, in most cases, found to be in a good agreement with fully nonlinear finite element analysis results. The presented model allows for a very efficient analysis with relatively high numerical accuracy and low computational efforts compared to fully nonlinear finite element analysis results. A number of applications have been described, with the aim of demonstrating the capability and versatility of the presented approach.