This study determined the chemical composition and evaluated the antioxidant activity and antifungal properties of essential oils of oregano (Origanum vulgare) and mint (Mentha arvensis) against the fungi Aspergillus flavus and Penicillium commune as possible alternatives for food preservation. The antimicrobial activity of both oils is shown by their minimum inhibitory concentration (4 mg/mL) for oregano oil, and (8 mg/mL) for mint oil, and minimum inhibitory dose (< 110 µl/L) for oregano oil, and (< 1500 µL/L) for mint oil. In addition, both oils presented antioxidant activity superior to 70% at the concentrations of 0.5 mg/mL for oregano oil and 30 mg/mL for mint oil after 360 min of reaction. As a control, the oils were evaluated for their cytotoxic potential using cells in culture and the method based on mitochondrial activity. Both oils were cytotoxic to both cell lines tested, with cells' survival rates less than 20% when in contact with 25 μg/mL of oils concentrations. Overall, the essential oils have activity against Aspergillus flavus and Penicillium commune, and their volatile components expressed high antifungal activity that expands their use for situations in which direct contact with the liquid is undesired. However, both essential oils showed high cytotoxicity.