As a first attempt, finite element (FE), genetic algorithm (GA) and particle swarm optimization (PSO) methods are mixed to maximize buckling load of stiffened laminated composite plate via finding optimum fibers orientation of the plate. The FE method is used to solve the higher-order shear deformation based equations of the plate. To improve the performance of genetic algorithms for solving the problem, the particle swarm optimization technique is added as an operator of the GA. Accuracy, convergence and applicability of the proposed approach are shown. Effects of the dimensions of the plate, the cross section shapes of the stiffener(s), number of layers of the plate and boundary conditions on the optimum results are investigated. (C) 2017 Elsevier Masson SAS. All rights reserved.