The development of science and technology during the past decade is characterized by intensive studies of the properties of nanoparticles and various ways for their practical application. Analyzing and generalizing studies, as well as a number of successful implementations of nanoindustry products, suggest that further progress in this direction will help to solve many problems facing humanity today. At the same time, there is no doubt that widespread application of nanotechnologies means the transition to a new level of scientific and technological progress in which its reverse side is full of new dangers associated with manifestations of properties and characteristics that were not yet known. Metal nanoparticles are among the most widely used, especially Fe3O4, which are of interest for practical applications. Therefore, the adverse effects of Fe3O4 nanoparticles must obviously be investigated on cellular organisms in order to assess the risks. As attractive model microorganisms for studying the influence of nanoparticles on molecular and cellular mechanisms, strains of the genus Rhodotorula can be used effectively for this purpose. Due to the cellular structure, functional organization and ability to synthesize antioxidant compounds such as carotenoid pigments, this unicellular eukaryotic organism can serve as a model for assessing cellular responses to nanoparticle toxicity and subsequent elaboration of detoxification strategies. In this context, the purpose of the research was to evaluate the effects of iron oxide nanoparticles on carotenoid content of Rhodotorula gracilis CNMN-Y-30 yeast strain. For impact assessment in the experiments we studied the changes induced by Fe3O4 nanoparticles with size of 50-100 nm (Aldrich product) with different concentrations of 0.5; 1.0; 5.0; 10.0; 15.0; 20.0; 25.0; 30.0 mg/L, on biosynthetic potential for carotenoid accumulation and β-carotene, toruline, torulorodine base components in Rhodotorula gracilis CNMN-Y-30 strain. According to the obtained results, the yeast response to the presence of nanoparticles was manifested by an increased toxicity effect on carotenoid pigment biosynthesis. Under the influence of concentration ranges 0.5...30.0 mg/L, it was observed a decrease of carotenoid content by up to 72.9% compared to control sample. To determine the degree of influence of nanoparticles on carotenoid content, the concentration was determined spectrophotometrically. The data indicated that the content of these pigments decreased directly proportional to the concentration of Fe3O4 nanoparticles (50-100 nm) introduced into YPD cultivation medium. Therefore, we can assume that Fe3O4 nanoparticles lead to blocking the carotenoid biosynthetic processes, which have been manifested by major changes in their content in yeast biomass. Using high concentrations of nanoparticles, the yeast cells may completely lose their pigment biosynthesis ability. By generalizing the results we can state that Fe3O4 nanoparticles (50-100 nm) have a high toxicity effect that places them in the hazard category - harmful substances.