The evolution of microorganism defense systems has led to intensive searches for new drugs extracted from various natural products to fight microbial infections. This study evaluated the antibacterial and antifungal activity of Lygodium venustum, a climbing fern. A phytochemical screening was performed using ethanol extract from leaves of L. venustum (EELV), detecting the presence of phenols, tannins, flavonoids and alkaloids. The test of Minimal Inhibitory Concentration (MIC) against Escherichia coli, Staphyloccocus aureus, Pseudomonas aeruginosa, Candida albicans, C. krusei and C. tropicalis was evaluated using the microdilution method, resulting in inhibitory concentrations of 1024 mg/mL. Using a subinhibitory concentration of 128 mg/mL of EELV, the modulatory potential of the extract was tested against multidrug-resistant clinical isolates, resulting in synergism when combined with Gentamicin and actually altering the phenotype of S. aureus from sensitive to resistant. The extract also increased the effect of the kanamycin against S. aureus. This was the first report of modulatory antibiotic activity by a member of Lygodium.