One of the main problems of the utilization of nanoparticles consist in the evaluation of the risks to human health and environment [Holsapple, 2005]. The given research aims to evaluation of the toxicity of nanoparticles with the utilization of yeasts in quality of experimental object. The relevance of the investigations was determined by the intense development of nanotechnology and application in numerous fields such as medicine, food industry, environment, et.al.; the solution of problems of the safety of nanomaterials and the necessity of the elaboration of safe and fast methods for the determination of the toxicity of nanoparticles [Yin et.al, 2013; Osmond et.al, 2010]. It is known that these yeasts are frequently used as complementary protein source. Pigmented yeast strains also can be considered as a source of antioxidant enzymes, such as superoxide dismutase (SOD) [Unlü, Takaç, 2012]. It serves as primary line of defense in destroying free radicals. The aim of the proposed paper was to evaluate the activity of an antioxidant enzyme superoxide dismutase at pigmented yeasts Rhodotorula gracilis CNMN-Y-03 at the cultivation in presence of ZnO nanoparticles with dimension <100 nm and concentration from 1 to 30 mg/L. Analyzing obtained results it was found that applying of selected nanoparticles has had positive effect on SOD activity. It was established that the highest values of SOD activity were determined at the concentrations 5 - 20 mg/L. Thus, indices of superoxide dismutase activity varied from 362 to 385 Units/mg protein what is with 128 and 142 % more than control sample. It is necessary to mention that the increase of the concentration of selected nanoparticles up to 30 mg/l contributed to the insignificant decrease of SOD activity, nevertheless enzyme values were more than of control. In this paper the application of nanoparticles has induced stress condition, inclusive oxidative stress and production of reactive oxygen species what caused significant increase in activity of antioxidant enzyme SOD. In present research it was demonstrated that nanoparticles of zinc oxide enhances the activity of this enzyme, which increases the degree of cell protection as adaptive response to oxidative stress. Acknowledgment: This research was financed by grant for young researchers 18.80012.51.16A from the Ministry of Education, Culture and Research and National Agency for Research and Development.