Plants of Heracleum sosnowskyi Manden. are rich in essential oil which might be of herbicidal potential. In this study, we examined 1) the content and chemical composition of H. sosnowskyi essential oil (EO) distilled from seeds and 2) the herbicidal effect of EO in a bioassay against germination of maize and five weed species. As a result, a 5.1% EO yield was obtained from the seeds of H. sosnowskyi. We identified sixty-two compounds of EO that constituted 96% of the total oil. Aliphatic esters were the main constituents of the EO, followed by aliphatic alcohols. The tested seeds showed different susceptibilities to the tested concentrations of EO (0.2 – 7.2 g L^-1). The most susceptible were Bromus secalinus and Avena fatua, and the most resistant were Echinochloa crus-galli and maize. Kernels of maize germinated normally up to a 0.6 g L^-1 dose of EO, and 20% of the seedlings were still germinating in the presence of 7.2 g L^-1 of EO. These findings suggest that the EO of H. sosnowskyi and its main compounds should be studied further in soil conditions for its herbicidal properties against A. fatua and weeds in maize.