Non-native waterbird populations are increasing through much of Europe with some species showing conspicuously successful invasions. Much uncertainty surrounds the potential impacts of invasive waterbirds on native waterbird communities and wetlands. Understanding the processes and phases of population and range expansion of non-native waterbirds, and their environmental drivers, is an important research topic to inform management of these species. This study investigates the trajectories of population and range expansion of the Egyptian Goose (Alopachen aegypticus) across the UK between 1993 and 2014, and the environmental and spatial drivers of population density and site occupancy for three representative time periods, using the British Trust for Ornithology’s Wetland Bird Survey (WeBS) data. Egyptian Goose showed an accelerating rate of occupancy of new grid cells (at 20-km resolution) over the time period of the study. There is no apparent reduction in the rate of spread of this species, insofar as through time there is an increase of both grid cell occupancy and of wetland area occupancy, although in the latter stages of expansion (post-2003) it appears that there is more of a filling out effect going on, at the same time as the increased rate of expansion. Environmental models supported the a priori hypothesis that waterbodies have a negative association with densities of Egyptian Goose, which was born out in the results. Environmental models also showed that rainfall was consistently negatively associated with density and presence/absence, whilst stately homes were shown to be consistently positively associated