Southeast Romania is one of the most important wintering areas for the IUCN-designated vulnerable Red-breasted Goose Branta ruficollis, where regular monitoring has been undertaken as a contribution to the international Red-breasted Goose monitoring scheme from 2012 to 2022. Simultaneous roost counts were undertaken from November–February, covering 17 key sites for the species in southeast Romania, and all major wetlands in the country were surveyed in mid-January as part of the International Waterbird Census. The species was found wintering entirely near large lakes and wetlands in the lowlands of southeast Romania, exclusively concentrated in two regions: Baragan and coastal Dobrogea. Between 2012 and 2022, national totals were estimated at between 8,660 and 23,783 individuals, with an average of 16,322 birds, which represents almost 30% of the global population. Population trends for the species in Romania over the same period are classified as “uncertain”. At the regional level, the 10-year period trend shows a moderate increase in Baragan region and a strong increase in coastal Dobrogea, but for the last five years the trend in both regions is uncertain. Solitary birds or small groups might be seen also in other wetlands across the western and eastern lowlands of the country for short periods of time, especially during migration. We found that 25% of observations of the geese were registered outside of the borders of the protected areas, in areas which may hold flocks of over 10,000 Red-breasted Geese. The current vulnerability of this population, and the uncertainty regarding its true global abundance and trends, highlights the need for continuous coordinated counts in the country, in order to understand how the species will adapt to the climate changes, which might have an influence on its total population size and distribution.