During the breeding seasons 2007−08 and 2008−09, I recorded a number of signs, which suggested to me the occurrence of polygyny in the Rufous-tailed Hawk (Buteo ventralis). Observations were made on the Adencul Hill in the Araucanía region, southern Chile. Signs of possible occurrence of polygyny were: (i) sightings of only one adult male and two adult female hawks ying together within an area that normally is occupied by one monogamous pair, (ii) the close proximity between the nest sites of the two female hawks (750 m in distance), (iii) frequent trips of the male hawk toward both nest sites, and (iv) records of both aggressive and tolerant interactions between the two female hawks. All these signs suggest that the male mated with both females, and it would represent the rst record of polygyny in the Rufous-tailed Hawk.