The Red-legged Cormorant (Phalacrocorax gaimardi) is a neotropical cormorant with a moderately small population and is currently categorized as “Near Threatened” by the International Union for Conservation of Nature. The Red-legged Cormorant is distributed only along the coasts of Peru, Argentina and Chile; however, the most important breeding population for this species occurs within a small area in Chile. Between 1998 and 2000, the entire breeding population size of the Red-legged Cormorant and its distribution in Chile were determined, but some areas were poorly surveyed. The breeding population sizes of the Red-legged Cormorant were surveyed along the Araucania coast, an area in south-central Chile not considered in previous studies. A total of 3,175 nests and 13,018 adults were distributed over 10 breeding colonies along the Araucania coast. Our results increased the known breeding population size of the Red-legged Cormorant in Chile by almost 62% (from 5,018–5,218 to 8,193–8,393 breeding pairs) and the rangewide population estimate by almost 43% (from 30,000 to 43,018 individuals). This area could be one of the most important breeding areas for this species throughout its range. Currently, the colonies of Piureo-Puaucho (1,506 nests), Nigue (1,009 nests) and Punta Ronca (Queule) (964 nests) represent almost 42% of the breeding population of this species in Chile, so these breeding sites should be a priority for conservation efforts.