The antimicrobial effect of oregano essential oil (OEO), grapefruit seed extract (GSE) and their combination on the growth and survival of foodborne pathogens (Salmonella Typhimurium and Listeria monocytogenes) were determined in poultry fillets under modified atmosphere packaging (30% CO2/70% N-2). In a preliminary experiment, OEO and GSE were used at concentrations of 0.05%, 0.1%, 0.5%, 0.8%, 1.0%, 1.5%, 2.0% and of 0.01%, 0.02%, 0.04%, 0.08%, 0.1%, respectively. Paper disc diffusion testing showed that OEO at 0.05%, 0.1% and GSE at 0.01%, 0.02%, 0.04%, 0.08% had weak antibacterial activity. In addition, due to the very strong odour and taste, poultry samples treated with OEO at 1.0%, 1.5%, 2.0% and the combinations were assessed with scores below the limit of acceptance. Thus, the levels of 0.5% and 0.8% of OEO and 0.1% of GSE were further used in poultry fillets. In this study, the pathogens were affected by OEO and GSE. L. monocytogenes was the most sensitive pathogen. In conclusion, the results of this study confirmed the possibility of using natural products with MAP in food production to prevent the growth of foodborne bacteria.