Longitudinal changes in the structure and properties of food webs are known to occur in river systems from mountains to lowland areas. However, it is still unknown how food web structure and properties change along the estuarine-coastal gradient. Highly resolved estuarine food webs were assembled for 30 sites in the Tagus estuary and adjacent coastal waters to investigate changes in food web structure and properties along 4 sections: upper estuary, middle estuary, channel and coast. This work confirmed the highly variable nature of estuarine systems, not only in terms of physicochemical and biological communities, but also in food web structure and network properties. The upper estuary stood out for having the highest variability for many food web properties. Overall, more significant differences were detected within this estuarinecoastal gradient than previously reported for river systems, and over a much smaller spatial scale.