An ethanol extract prepared from the gametophyte Chilean native moss Sphagnum magellanicum was dried out, weighed and dissolved in distilled water. This extract was then assayed for its antibacterial activity against the G(-) bacteria Azotobacter vinelandii, Erwinia carotovora subsp. carotovora, Enterobacter aerogenes, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Vibrio cholerae, and the G(+) bacteria Staphylococcus aureus subsp. aureus, and Streptococcus type b. The growth of the cultures of E. carotovora subsp. carotovora, and V. cholerae was inhibited at a concentration of 581mg/ml of extract, while the cultures of E. coli, S. typhi and Streptococcus type b were inhibited at a concentration of 1.16 mg/mL of extract. The concentration of phenolic compounds was 4.294 mg/mL; the presence of vanillic, chlorogenic, syringic, caffeic, gallic, 3-4 hydrozybenzoic, p-coumaric and salicylic acids was identified using RP- High Pressure Liquid Chromatography.