Jackfruit (Artocarpus heterophyllus Lam.) is a fruit of tropical and subtropical zones of the world, is an important source of phytochemicals (phenolic acids, flavonoids and tannins). Several studies have associated phytochemicals with antioxidant and antimicrobial properties. The objective of this work was to analyze the polyphenolic content, the antioxidant and antifungal properties of jackfruit extracts on phytopathogenic fungi. Two phenolic extracts of jackfruit of different maturity level (J1-J2) were used. The total polyphenol content (TPC) was determined by Folin-Ciocalteu method and total flavonoids (TFC) by the aluminum chloride method, the free radical trapping potential was measured using FRAP and ORAC methods. The results showed a TPC of 844 and 1,178 mgEAG/100 g and TFC of 37 and 68 mgQE/100 g, of dry jackfruit, the antioxidant potential analysis by FRAP was 7,575 and 8,691, by ORAC was 13.369 and 14.728 µmol Trolox/100 g, of dry jackfruit for J1 and J2 respectively. Additionally, it was observed that the phenolic extracts of jackfruit reduced the mycelial growth of: Penicillium digitatum (20-14%), Geotrichum candidum (56-55%), Aspergillus niger (72-67%) and Botrytis cinerea (100%-100%) for J1 and J2 respectively. We conclude that regardless of the degree of maturity, jackfruit has antioxidant and antifungal properties on phytopathogens important in agriculture.