The objective of the present study was to investigate the in vitro antibacterial activity of the extracts and their fractions obtained from either the flowers or the leaves of Helichrysum plicatum DC. subsp. plicatum (Asteraceae), by studying inhibition of the growth of a dangerous food pathogen, Escherichia coli O157:H7. The antibacterial effects of the ethanol and water extracts of the flowers and leaves were examined first. Subsequently sub-extracts of the flower ethanol extract (FEE), which was found to be the most effective extract, were examined. As a result, the antibacterial effect of FEE was found to be stronger than that of the chloroform and ethyl acetate sub-extracts. This may due to synergistic activity of several components of the ethanol extract of the flowers.