The antimicrobial activities of monoacylglycerols (MAGs) with different lengths of hydrophobic hydrocarbon chains (1-decanoylglycerol, 1-undecanoylglycerol, 1-dodecanoylglycerol, 1-tridecanoylglycerol, 1-tetradecanoylglycerol) were investigated. Food undesirable bacterial strain Bacillus subtilis DMF 2006 and mould strains Aspergillus niger DMF 0501 and Fusarium culmorum DMF 0103 were used as indicator strains in order to determine antimicrobial properties of monoacylglycerols. The strongest antibacterial effect was caused by 1-undecanoylglycerol, 1-dodecanoylglycerol, 1-tridecanoylglycerol. These substances inhibited growth of Bacillus subtilis DMF 2006 for more then 10 days of incubation at the concentration of 0.05 mg/ml. Concentrations of 0.05 and 0.07 mg/ml of 1-decanoylglycerol, 1-undecanoylglycerol, 1-dodecanoylglycerol reduced the mycelium formation of Fusarium culmorum and Aspergillus niger. Higher concentrations (0.1 and 0.5 mg/ml) of these three substances inhibited spore germination. Knowledge of these properties brings new approach in food preservation where the substitute of chemical substances, such as sorbic and benzoic acids and their salts is in demand.