James's Flamingos (Phoenicoparrus jamesi), also known as Puna Flamingos, are distributed primarily in the Andean wetlands of southern South America during the breeding season, and dispersed through the lowland wetlands in Argentina during the non-breeding season. However, the main sites where they concentrate during the non-breeding season still remain unknown. Here, we report the first records of James's Flamingos observed in two consecutive years (two adults in Aug 2010, one adult and two subadults in Jul 2011) at Laguna Melincué, a Ramsar site in Santa Fe Province, Argentina (33° 25′ S, 61° 28′ W, 84 m asl). James's Flamingos were feeding in a mixed flock of Andean and Chilean flamingos (Phoenicoparrus andinus and Phoenicopterus chilensis, respectively). Our observations constitute the southernmost record for presence of this flamingo species at any lowland site and indicate the high dispersal ability of this species and its plasticity in occupying different wetland types during the non-breeding season.