Ports facilitate a waterborne transport which is the backbone of international trade, and thereby the global economy. This vital position in the international trade coupled with their nature as a limited capacity infrastructure enabled ports to be a significant market actor that is susceptible to possess market power. Port operators may acquire a dominant position in the relevant markets concerned. The acquisition of a dominant position may not be a concern in itself. However, this dominant position may contain an inherent element of potential capacity of abusive behavior which may compromise effective competition in the port industry. Despite its obvious importance to the economy, the application of competition rules to port operators has always been complicated due to various factors. Considering the high significance of ports in facilitating the international trade of EU and the free movement of persons and goods within the Union, this study focuses on determining the extent of application of the EU competition rules for the sector of port operators. Under this general purpose, this thesis will analyze the rule prohibiting abuse of dominant position in port operators; in particular, examining the core points of this rule such as ‘undertakings’, ‘relevant market’, ‘dominance’ and ‘abuse’; and finally, determining how and to what extent the rule against an abuse of dominant position could be applicable to port operators.