The increasing consumer demand for safety and long-term products motivates the packaging industry to produce antimicrobial packaging. The task of the antimicrobial packaging is not only the inhibition of growth of the pathogenic microflora, but also the maintenance of sensory characteristics of the product for a long time. The aim of the study was to evaluate antimicrobial properties of modified PLA foils against Gram-positive and Gram-negative bacteria. Biodegradable PLA foils were covered 10% ethylcellulose (EC) as carrier and commercial essential oils from fennel, rosemary and caraway as active substances. Antimicrobial properties were tested against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The study was conducted using the American method ASTM E 2180-01. The results of experiments showed that modified essential oils PLA foils reduced the amount of Gram-positive and Gram-negative bacteria. The best antibacterial properties would have PLA foil coating 10% EC with 50 mg/dm2 of fennel essential oil.