Territorial competitiveness is a fundamental concept of local economy and development. It is a set of factors and characteristics that determine the ability of territories (city, province, or region) to prosper economically, socially and culturally. This concept goes beyond economic competitiveness and includes aspects related to quality of life, innovation, sustainability and social cohesion: a territory becomes competitive when it is able to face market competition while ensuring environmental, economic, social and cultural sustainability based on networking and inter-territorial forms of articulation. A competitive region is able to attract investment, talent and businesses, creating an environment conducive to economic growth and the wellbeing of its community. The aim of this paper is to describe a methodology for assessing the territorial competitiveness of the Italian provinces and the impact that railway investments can have on it. Indeed, it is important to note the impact of rail investment on the competitiveness of an area, in terms of economic and employment growth, fostering integration and social cohesion, and providing new development opportunities for the population and businesses. Moreover, in this paper it will be presented the case study of the Palermo-Catania high-speed rail link and the evaluation of the impact of this investment on the competitiveness of the Sicilian territory. This investment aims to upgrade the Palermo-Catania railway connection by improving the Fiumetorto-Bicocca section to enlarge the current single-rail capacity and increase the speed limit to 200 km/h. The Palermo-Catania case study and the impact assessment of the new line have already been examined in the paper “Wider Effects of Railways—The Palermo-Catania High-Speed line, Italy”, in which the individual effects of the Wider Economic Impacts, Accessibility, Contribution to Reducing Inequalities and Agglomeration Effect were examined: Economic and Employment Impact, Accessibility, Contribution to the Reduction of Inequalities and Agglomeration Effect. In this publication it will be possible to observe how some of these impacts can affect the Sicilian competitiveness. The competitiveness of an area cannot be measured quantitatively by means of a one-dimensional indicator. It is therefore necessary to use methods that allow the multidimensionality of the phenomenon to be taken into account. To this end, it is possible to define a composite indicator characterised by a hierarchical structure based on simple, measurable variables that make up the different dimensions. These dimensions in turn make up the competitiveness indicator. Rete Ferroviaria Italiana has constructed a composite index of territorial competitiveness at the provincial level, composed by 8 specific composite indicators (dimensions), that can effectively summarise the phenomenon of territorial competitiveness. In particular: The paper presents the methodology used to construct the complex indicator and its application to the case study of the new Palermo-Catania link.