Abstract: This paper presents the practical implementation of Phase-Shifting Transformer (PST) model into an Optimal Power Flow (OPF) problem by using the Matlab optimization toolbox. The complexity degree related to the proposed implementation is equivalent to that required by commercial optimization packages for solving optimization models, but with the advantage that Matlab is commonly the available software for research and academic purposes in electric engineering. Thus, this hugely reduces the time to the implementation, and for obtaining results of an OPF analysis of power systems with embedded FACTS devices, in this case with the Phase-Shifting Transformer model. The reliability of the proposed implementation is proved by comparing the PST-OPF solution of the 5-node system with reported results in the open literature. In order to illustrate numerically the prowess of the proposed Matlab based implementation to solve the PST-OPF model, a numerical example with the 10-machine 39-bus New England test system is presented.