Antifungal activity of Bacillus coagulans creates the possibility to use this microorganism in biological control of fungal plant pathogens. Activity of Bacillus coagulans (No 6), isolated from lupine compost, against seven pathogenic species of indicator fungi: Bipolaris sorokiniana, Trichothecium roseum, Rhizoctonia solani, Sclerotinia sclerotiorum, Fusarium oxysporum, Fusarium solani and Fusarium culmorum were examined in this work. Ergosterol assessment and counting colony forming units (CFU) carried out determination of fungal growth. The addition of Bacillus coagulans to culture of fungi resulted in inhibition of ergosterol biosynthesis in mycelium. The strongest inhibition in all tested fungal plant pathogens was observed when Bacillus coagulans was co-inoculated at the beginning of culture. The decrease of ergosterol level did not always correlate with the decrease of CFU.