By using plant extracts in the biological control of fungal plant diseases, it is possible to reduce the negative effect of agrochemicals and the problem of resistance of the target microorganisms. Because of that, the focus of interest is the discovery of plant extracts that have antifungal properties and are not toxic to the environment in the biological control against economically important phytopathogenic fungi. The aim of the research is in vitro testing of the effect of aqueous cinnamon bark extract on the growth and development of the mycotoxigenic fungus Fusarium sporotrichioides, which causes economically significant damage to a wide range of plant cultures. For the purpose of conducting research, the aqueous extract of cinnamon bark was obtained using ultrasonic-assisted extraction, and the presence of antifungal compound content was proven by phytochemical tests. The research results confirm a significant inhibition of the F. sporotrichioides growth by 10.4 % and 70 % when it was grown on a medium with 3 % and 5 % of extract. The antifungal effect of the extract was proven by a microscopic analysis of the pathogen, which revealed significant deformations of hyphae and a change in the color of the mycelium after seven days of growth at a concentration of 5 %, which led to an almost seven-fold greater inhibition of pathogen growth compared to a 3 % extract. Based on the obtained results, the aqueous cinnamon bark extract shows a fungistatic effect on the micellar growth and development of the pathogen F. sporotrichioides, thus also the potential possibility of application in the biological control of this economically important phytopathogenic fungi.