The introduction of soybean cultivation in South Moravia (Czech Republic) has created new ecological habitats for weed species. Weed communities were surveyed using the phytosociological relevé method on 491 ha of operational land under soybean cultivation. Although soybean crops exhibited relatively strong competitive ability against weeds under field conditions, certain species were able to establish successfully. Among invasive neophytes, Bassia scoparia demonstrated the capacity to persist even within a dense crop stand. Naturalized archaeophytes that are successful even with high cover include Datura stramonium, Euphorbia exigua, Mercurialis annua, Panicum miliaceum, Setaria pumila, and Solanum nigrum. The cultivation of new crops creates opportunities for the spread of other weed species and may contribute to the invasion of non-native species where they did not previously occur.