Traditional packaging concepts are reaching their limits in enhancing food safety, quality and shelf life. Active, antimicrobial sachets containing different concentrations of oregano essential oil (OEO) were developed, and their antimicrobial efficiency was evaluated on agar medium -against Escherichia coli, Salmonella Enteritidis and Penicillium sp. -and on sliced bread -against yeasts and molds. Residual OEO on treated bread was quantified by gas chromatography-mass spectrometry. Bread slices were also evaluated as to texture and sensory properties. Sachets containing OEO showed in vitro antimicrobial effect against the tested microorganisms, as well as reduced the growth rates of yeasts and molds on sliced bread. Compared with untreated samples, γ-terpinene and ρ-cymene contents on treated bread increased throughout storage, whereas their acceptance was reduced. Our findings indicate the potential application of antimicrobial sachets as an antimicrobial packaging system for sliced bread preservation.