Abstract The essential oil from the fresh leaves of Callistemon speciosus (Sims) DC. was isolated by hydrodistillation. Thirty-one volatile compounds (relative amount >0.1%) were separated and positively identified by GC (FID) and gas chromatography-mass spectrometry (GC/MS). Major constituents were 1,8-cineole (55%), α-pinene (19%), α-terpineol (4.1%), and α-phellandrene (3.0%). The oil presented a mean lethal concentration against Artemia franciscana of 56.7 μg/L and 39.8 μg/mL after 24 and 48 h exposition, respectively, and had a mild but significant effect on the crustacean elongation