Extracts from Ailanthus altissima (Mill.) Swingle (Simaroubaceae) contain quassinoids with herbicidal properties. Therefore, the purpose of our work was to study the effect of A. altissima ethanolic extract on some weeds of the Poaceae family. We used as test objects a mixture of plants of the Poaceae family from Lolium multiflorum Lam. and Lolium perenne L. taken in equal amounts, which was sown under solarium conditions and provided with regular watering. It was found that 2.5 and 5.0% A. altissima extract significantly reduces the length of the roots of weeds in comparison with the control (by 14.02-28.54%; LSD=1.05 at p≤0.05). At the same time, a 5.0% extract from A. altissima also significantly (by 10.68%) compared with the control and at the level of a chemical standard reduces the height of the stems of Poaceae plants. The mass of treated plants with A. altissima extract is reduced by 1.9-2.2 times in comparison with the control and was at the level of the chemical standard (LSD=0.12 at p≤0.05). Thus, the extract from A. altissima has herbicidal properties against weeds L. multiflorum and L. perenne of the Poaceae family, which is expressed in a decrease in the height of the stems, inhibition of root growth and, as a result, in a decrease in the total weight of plants. The authors are grateful to the Ministry of Education, Science, Research and Sport of the Slovak Republic for supporting researcher’s mobility of Elisovetcaia Dina, PhD within the bilateral scholarship program for 2022-2023.