Eryngium foetidumL. is an edible plant widespread in Amazonian cuisine and its leaves have high levels of promising phenolic compounds for the production of extracts to be used as natural antioxidant additives. In this study, the in vitro scavenging capacity of three freeze-dried extracts ofE. foetidumleaves, obtained by ultrasound-assisted extraction using green solvents [water (H2O), ethanol (EtOH), and ethanol/water (EtOH/H2O)], was investigated against the most common reactive oxygen species (ROS) and reactive nitrogen species (RNS) generated in both physiological and food systems. Six phenolic compounds were identified, chlorogenic acid (2198, 1816 and 506 μg/g) being the major compound for EtOH/H2O, H2O, and EtOH extracts, respectively. AllE. foetidumextracts were efficient in scavenging all the ROS and RNS (IC50= 45–1000 µg/mL), especially ROS. The EtOH/H2O extract showed the highest contents of phenolic compounds (5781 μg/g) and showed the highest efficiency in scavenging all the reactive species, with high efficiency for O2•−(IC50= 45 μg/mL), except for ROO•, for which EtOH extract was the most efficient. Therefore,E. foetidumleaf extracts, especially EtOH/H2O, showed high antioxidant potential to be used as natural antioxidants in food formulations and are promising for nutraceuticals products.