Fusariosis is an economically significant disease of a variety of crops that causes ascomycete fungi of the genus Fusarium. Fusarium species are also distinguished by the production of a large number of mycotoxins. F. avenaceum causes class and rot of wheat and barley root rot, and produces several mycotoxins that can harm human and animal health. F. equiseti appears as a colonizer of old and damaged plant tissue and as a weak parasite on wheat, but is characterized by high mycotoxin production. Known bio-factors, ascomycetes of the genus Trichoderma also contain species that mycoparasize mycelium of Fusarium species. A collection of T. koningiopsis KP / AR was isolated from the collection of indigenous isolates, whose antifungal effect on Fusarium species is unknown. The paper investigates the antifungal influence of the indigenous isolate T. koningiopsis KP / AR, ie antibiotic suppression and mycoparasitic micellar culture of the mentioned Fusarium species. The experiment was set up in the laboratory of the Department of Phytopathology, Faculty of Agronomy, University of Zagreb. The experiment was performed in vitro using a double culture method for testing mycoparasitization and a double culture method for the determination of volatiles (antibiosis). 4 and 7 days old fungal cultures were used and the KP / AR interface with each pathogen was performed. The experiment was set on a random block layout in 5 variants with 3 repetitions. In the fourth day incubation assay, the inhibition index for F. equiseti was 7.33% and for F. avenaceum was 0%. On the seventh day of incubation, the F. equiseti inhibition index was 43.52% and that of F. avenaceum was 35.31%. In the fourth day incubation antibiotic, the F. equiseti inhibition index was 3.3% and that of F. avenaceum was 5.56%. On the seventh day of incubation, the index of inhibition of F. equiseti was 17.02% and that of F. avenaceum was 33.32%. Based on the results of the experiment, the KP / AR isolate showed non-significant antifungal activity. The KP / AR isolate also showed a non-significant antibiotic activity.