The essential oil from leaves of Eremanthus erythropappus (DC.) MacLeish (Asteraceae) collected in South-eastern Brazil was extracted using a combination of water and steam distillation and investigated by chromatography/mass spectrometry (GC-MS). The sesquiterpene hydrocarbons were predominant (46.6%), followed by oxygenated sesquiterpenes (29.3%) and monoterpene hydrocarbons (18.8%). The major compounds were (β)-caryophyllene (29.3%), caryophyllene oxide (22.1%) and β-pinene (12.8%). The allelopathic activity of E. erythropappus essential oil on the seed germination and radicle length of seedlings was evaluated in lettuce (Lactuca sativa L.), tomato (Lycopersicum esculentum Mill.) and in two field weeds (field mustard – Brassica rapa L. and hairy beggarticks – Bidens pilosa L.). Among the weed species tested, the most significant inhibition of seed germination was observed in field mustard, as measured by the half–minimal inhibitory concentration, IC50 (IC50=26.5μL mL–1), and the most significant inhibitory effect on radicle length of seedlings was observed in seedlings of hairy beggarticks (IC50=16.3μL mL–1). In contrast, the lowest allelopathic effects of E. erythropappus essential oil on seed germination and radicle length of seedlings were observed in tomato (IC50=>200μL mL–1 and 130.1μL mL–1 respectively) and lettuce (IC50=97.1μL mL–1 and 35.1μL mL–1 respectively). These results revealed significant allelopathic potential of E. erythropappus essential oil against weeds, but minimal effect on lettuce and tomato germination, and thus suggests it is feasible to use E. erythropappus sustainability as an eco-friendly bioherbicide in cropping settings.