This paper develops heuristic approaches to define the market and measure concentration in the inland transhipment market where different terminal operators compete. These approaches can be used by policymakers to implement more effective policies that could lead to an increase in the market share of intermodal freight transport (IFT). The first approach segments the market using a transport cost analysis. The second approach uses the total trade and the aggregate throughput of the terminals in each IFT demand area. The similarity in results validates the two approaches, suggesting that they can both be used in situations of limited data availability. Applying these approaches to the IFT network of the European Union, we find that inland transhipment markets in the EU are oligopolistic in structure and thus highly concentrated. In general, the north of the EU shows less concentration compared with the central and southern regions of Europe. According to the second approach, transhipment markets have a slightly higher degree of concentration compared with the first approach. Such concentration needs more attention from policymakers so as to develop policies to increase competition and to make economic policies more effective.