This thesis describes project management methodology implementation in a consulting company and examines the impact of this methodology on key success factors of the company. The theoretical part deals with issues related to project management implementation in a company and describes well-known methods and standards in this area while focusing on PRINCE2 methodology, which has been chosen for the implementation. The theoretical part continues by describing the process of creating system dynamics models, which allowed the key success factor models to be created as tools for evaluation of the methodology implementation impacts. The practical part of this thesis describes the background for the methodology implementation project and then the implementation itself in detail. The practical part continues by showing and describing the created key success factor models. In the end, the methodology impacts evaluation is carried out, analyzing changes in separate elements of the model breakdown.