DOI: 10.7764/RDLC.18.2.323Buckling analysis of arches is an important issue of the design of timber structures containing such structural elements. In the article an analytical and an approximate solution is proposed for lateral torsional buckling analysis of truss-braced timber arches. Application of the proposed methods was introduced by a numerical example. Critical forces calculated by the analytical and approximate methods were also compared to the results of numerical analysis, proving the sufficient accuracy of the different solutions. The effect of different timber truss-bracing solutions on the critical force of the examined timber arch was analysed using the introduced analytical method. The critical force of the examined truss-braced arch was up to two orders of magnitude greater than the critical force without bracing, proving that the consideration of the lateral bracing is important during the design because on the one hand, it ensures the static conformity of the structure, and, on the other hand it leads to more economical structural configuration in terms of lateral torsional buckling. Both analytical and approximate method presented in the article can be used to determine the optimal geometric configuration of the bracing truss in order to maximize the critical force of the laterally braced arch.