Ports are essential for global trade, but there are growing concerns about their impacts on the local economy. Insight in these local economic impacts of ports and inter-regional spillovers is crucial for future investment decisions and local acceptance of port development. Inter-regional spillovers from port activities are commonly assumed in the academic literature on port economics, but rarely ever quantified. This article fills this gap by quantifying the backward linkages of four large ports in NorthWest Europe: Rotterdam, Antwerp, Hamburg and Le Havre. To assess the extent and distribution of inter-regional economic spillovers, we disaggregate national input/output-tables to the level of the functional port area and calculate the relevant Leontief multipliers. The results in this paper suggest a wide range of Leontief multipliers with different inter-regional patterns. The ports of Rotterdam and Antwerp have smaller overall multipliers but relatively large impacts on their own regional economies, in particular on the petro-chemical sector. In contrast, the ports of Hamburg and Le Havre have higher overall multipliers and show relatively high impacts on regions further away from the port, such as Bavaria and Ile-de-France. The policy implications of these results are discussed.