Field and laboratory studies determined the effect of intercrop plants (rye, buckwheat, white mustard and sunflower) used in carrot cultivation on the occurrence of Clonostachys spp., Albifimbria spp., Trichoderma spp. and Penicillium spp. in the soil and their antagonistic activity. Rye and white mustard were the most effective in limiting the occurrence of soil-borne fungi. Those plants caused an increase of the population of the studied antagonistic fungi. Buckwheat and sunflower promoted the development of antagonists a little worse. The antagonistic activity of the aforementioned fungi was the highest after using rye and white mustard and slightly after buckwheat and sunflower. Those fungi were the most effective in inhibiting the growth of Altenaria dauci, A. radicina and Sclerotinia sclerotiorum pathogenic towards carrot.