Abstract The volatile constituents from leaves of Callistemon viminalis (Gaertn.) G Don grown in Colombia was studied by GC and GC-MS. Eighty-nine compounds were identified, of which the most prominent were 1,8-cineole (39.4 %), α-pinene (8.9 %), α-phellandrene (8.6 %) and α-terpineol (6.1 %). The in vitro antibacterial activity of the essential oil was studied against seven bacteria strains using the disc diffusion method. The essential oil exhibited strong zone of inhibitions against some bacteria such as Staphylococcus aureus (>20 mm), Listeria innocua (14 mm), and Enterobacter sakazakii (18 mm). Key words: Callistemon viminalis essential oilantibacterial activity1,8-cineoleα-pineneα-phellandreneα-terpineol