The competitiveness of seaports is predominantly affected by factors external to the ports themselves, connected mainly with the quality of the hinterland and foreland infrastructure. Measures taken in these areas are reflected in the main objectives of the port strategies. Concurrently, the measures may have adverse environmental impacts (pollutant emissions, noise, land occupancy, etc.) and deteriorate the life quality of the port city’s communities. Therefore, measures taken by seaport authorities to improve their competitiveness must also heed the idea of sustainable development (sustainable port strategy). The answer to this challenge is the idea of green ports, being an element of the corporate social responsibility (CSR) strategies of seaports. One of the elements of this concept is promoting more environmentally friendly transport modes/transport chains in serving the hinterland as an alternative to road transport. Inland shipping is the most environmentally friendly and also cost-competitive mode of transport. Therefore, a modal shift from road to inland waterways is one of the elements of the European Union sustainable transport policy, as well as also gaining importance in the development policies of seaport authorities as an element of a green port strategy. However, this issue has been relatively rarely addressed in the seaport economics literature. In particular, there has been a lack of studies that would make it possible to answer the question of what kind of action should be taken by seaport authorities in order to increase the share of inland shipping in hinterland transport. This article aimed to develop a concept of a promotion policy to be applied by seaport authorities to increase the share of inland shipping in hinterland transport. The study used the elements of a multiple case study design method which included the following seaports: Antwerp, Rotterdam, Hamburg, and the Marseilles–Fos port complex. This article was dedicated to identifying, analyzing, and classifying the policies implemented by these European seaports to promote inland waterway transportation. The research showed that these actions were quite similar in terms of their scope. The actions were classified as external and internal initiatives. The most common external actions included initiatives that improved the quality of inland waterways and the quality of shipping connections with the hinterland. Internal initiatives focused on improving the port’s infrastructure for barges and on implementing an appropriate information policy. The presented concept of a promotion policy can be a road map for all port authorities aiming to improve the quality of inland shipping as a mode of hinterland transport.