This study identified the compounds obtained from four native Dehesa plants, which were holm oak, elm, blackberry and white rockrose, and evaluated their ability to inhibit the growth and production of aflatoxins B1and B2of two strains of mycotoxigenicAspergillus flavus. For this purpose, phenolic compounds present in the leaves and flowers of the plants were extracted and identified, and subsequently, the effect on the growth ofA. flavus, aflatoxin production and the expression of a gene related to its synthesis were studied.Cistus albiduswas the plant with the highest concentration of phenolic compounds, followed byQuercus ilex. Phenolic acids and flavonoids were mainly identified, and there was great variability among plant extracts in terms of the type and quantity of compounds. Concentrated and diluted extracts were used for each individual plant. The influence on mold growth was not very significant for any of the extracts. However, those obtained from plants of the genusQuercus ilex, followed byUlmussp., were very useful for inhibiting the production of aflatoxin B1and B2produced by the two strains ofA. flavus. Expression studies of the gene involved in the aflatoxin synthesis pathway did not prove to be effective. The results indicated that using these new natural antifungal compounds from the Dehesa for aflatoxin production inhibition would be desirable, promoting respect for the environment by avoiding the use of chemical fungicides. However, further studies are needed to determine whether the specific phenolic compounds responsible for the antifungal activity ofQuercus ilexandUlmussp. produce the antifungal activity in pure form, as well as to verify the action mechanism of these compounds.