A 23.1m female blue whale stranded on 29 April 1992 in southern Brazil (33degree45'S), representing the first confirmed stranding of the species in Brazil and the second recent stranding in the southwest Atlantic. Morphological, biological, and osteological data were collected. Baleen plates were infested with commensal copepods Balaenophilus unisetus. The intestine was infested by acanthocephalan parasites Bolbosoma sp. The vertebral formula was C7+D15+L15(14)+Ca27(28) = 64. Some observed characters were closer to those of pygmy blue whales (e.g. length of tail section) and others were similar to those of 'true' blue whales (e.g. rostrum width at the middle of its length). The scarcity of osteological studies on blue whales worldwide and the dubious characters of this specimen made it difficult to assess its definite taxonomic identity.