A primary failure mode for thin-walled steel members is lateral-torsional buckling (LIB), in which steel cantilever beams experience nonuniform twisting and buckling about their weak axes. Analytical and numerical studies related to the elastic LTB of cantilevers abound. However, comprehensive analytical and experimental studies focusing on the inelastic L713 behaviour of cantilevers are rare. Therefore, this study intends to establish a numerical procedure verified with experimental results to evaluate the inelastic LTB strength of steel cantilevers with an I-section. First, an experimental study was performed, in which nine steel cantilever beams with different slenderness and load-height levels were tested. Load-displacement behaviours of steel cantilevers were investigated by measuring lateral and vertical displacements and rotations under the effect of a monotonic end-point load. Subsequently, a two-step numerical procedure is introduced. The elastic LTB loads and the related mode-shapes were determined in the first step, and the nonlinear load-deflection behaviours were evaluated in the second step based on the Riks method. Finally, numerical and experimental results were compared, thereby demonstrating that the presented numerical analysis can be used for predicting the buckling loads, vertical displacements, and torsional rotations at an acceptable level in the design stage. (C) 2020 Elsevier Ltd. All rights reserved.