A large deflection, semi-analytical method for pre- and postbuckling analysis of stiffened plates with a free edge is presented. The stiffeners can be oriented in both directions parallel and perpendicular to the free edge, and the stiffener spacing can be arbitrary. Both global and local buckling modes are captured by using a displacement field consisting of displacements representing a simply supported, stiffened plate and an unstiffened plate with a free edge. The out-of-plane and in-plane displacements are represented by trigonometric functions and linearly varying functions, defined over the entire plate. The formulations derived are implemented into a FORTRAN computer program, and numerical results, including load-displacement curves, stress plots and displacement shapes, are compared with results by finite element analysis for a variety of plate and stiffener geometries. Relatively high numerical accuracy is achieved with low computational efforts. In addition, introductory investigations of ultimate strength limit (USL) predictions computed by the present model are presented.