This study was conducted in both field and greenhouse settings. The experiment featured five replications and followed a randomized plot design and was replicated twice in both 2020 and 2021. In the experiment, cruciferous plant extracts were applied at concentrations of 2%, 6%, and 10% in pots, each containing 20 field dodder seeds and a single eggplant seedling. The purpose of this study was to assess the allelopathic effects of these extracts on various parameters, including field dodder seed germination, field dodder fresh biomass, eggplant height, the total number of eggplant branches per plant, and the number of infected eggplant branches per plant. Additionally, the cruciferous plant samples underwent GC-MS analysis to determine their content of isothiocyanate compounds. The cruciferous plant extracts did not negatively affect eggplant height or the number of eggplant branches per plant. However, all the cruciferous plant extracts led to a reduction in the field dodder seed germination rate. The treatment involving turnip extract at a 10% concentration demonstrated the highest efficiency, resulting in a reduction of 55.72% in the field dodder seed germination rate. Moreover, it is noteworthy that the allelopathic effects of cruciferous plants increased in tandem with increasing extract concentrations. The results of the GC-MS analysis indicated that turnip exhibited the highest percentage of isothiocyanate compounds among the cruciferous plants, accounting for 56.6% of the total, whereas black radish exhibited the lowest percentage at 29.2%.