Port competition is a complex phenomenon that is inextricably linked to the port selection decisions of hinterland and maritime port users. To effectively analyze port competition and formulate strategies, it is essential to adopt a holistic perspective that considers the entire port system through a supply chain lens. Existing research on port competition has largely focused on constructing separate port choice models for hinterland and seaward considerations, or developing unified port choice models that do not distinguish between user groups. However, these approaches fail to account for the interdependent relationship between the port choice behaviors and port competitiveness of hinterland and seaward port users within a single port. In this study, we address this gap in the literature by proposing an integrated model that leverages port choice models of hinterland and maritime port users, along with their respective port preferences, within a multicriteria decision analysis-non-cooperative game theory framework. This integrated model enables a comprehensive examination of port selection and inter-port competition from a unified perspective. In addition, we construct a two-player, three-strategy non-cooperative game theory model in which hinterland and maritime perspectives are considered distinct game participants. Applying the proposed integrated multi-criteria decision-making port competition theory model to container ports, we find that Busan Port exhibits the highest overall competitiveness, followed closely by Yeosu Gwangyang Port and Incheon Port. The Nash equilibrium solution for all participants in both simultaneous and sequential games is confirmed to be the choice of Busan Port for both hinterland and maritime considerations. These findings suggest that Incheon Port and Yeosu Gwangyang Port, which benchmark the Nash equilibrium solution, should prioritize the enhancement of port selection factors according to their relative importance, particularly those where they fall short compared to Busan Port. Overall, this study provides a comprehensive understanding of port selection and a game theory-based port competition framework from the perspective of port users in the context of container ports. The findings of this study can support the strategy formulation of port authorities and port operators. However, future research could build more realistic models that categorize inland shippers by region and ocean carriers by route to obtain more practical outcomes