The plants have investigated in the search for new substances against microorganisms resistant to current pesticides and antibiotics. The aim of this research was to evaluate the existence of antiphytopathogenic properties of organic extracts from the leaves of amaranth (Amaranthus viridis L.), Amaranthaceae, popularly known as caruru. The hexanic, dichloromethanic, ethylic acetate and ethanolic extracts were obtained, respectively with yields of 2.2, 2.4, 3.2 and 3.6% (m/m). These extracts were used to determine the Minimum Inhibitory Concentration (MIC), through dilution technique using 96 well microplate. After reading the CIM in wells where no fungal growth was observed, the Minimum Fungicidal Concentration (MFC) was determined on plates containing dextrose Sabouraud agar. The experiments with the extracts of Amaranthus indicates activity against the fungi Colletotrichum musae (Berk. and Curt.) Arx, causing anthracnose of banana and against Fusarium solani f. sp. piperis responsible for fusariosis in black pepper. In relation to Colletotrichum musae extracts obtained with dichloromethane, ethyl acetate and ethanol, the MIC ranged from 15.6-250.0 μg mL-1. The hexanic, ethylic acetate and ethanolic extracts showed activity against Fusarium solani with MIC ranging from 31.2-250.0 μg mL-1. Through this research was showed the presence of antifungal constituents in extracts of Amaranthus viridis L., revealing its potential antimicrobial effect against these two phytopathogenic strains tested.