The purpose of the research was to determine the effect of TiO2NPs on biomass production of cyanobacterium Spirulina platensis CNMN-CB-02 during the cultivation cycle under laboratory conditions. The essential parameters specific to spirulina culture were monitored: biomass accumulation during the cultivation cycle and changes in the protein content into biomass. Spirulina was grown on the optimized mineral medium, supplemented with titanium oxide nanoparticles in a concentration range of 0.5-30 mg/L (9 concentrations). The biomass content was assessed spectrophotometrically using a calibration curve. The protein content in biomass was determined spectrophotometrically by Lowry method based on the reaction of Cu+, produced by the oxidation of peptide bonds, with Folin-Ciocalteu reagent. The experimental variants were compared with the biomass of the control samples. Analysis of the amount of biomass established a stimulating effect of TiO2NPs on culture productivity for most of the applied concentrations of nanoparticles. The minimum concentration of 0.5 mg/L titanium oxide nanoparticles increased biomass production by 19%. For concentrations from 1.0 to 30 mg/L, an increase in biomass content of 30-42% was determined compared to control samples. To confirm the stimulating effect of nanoparticles or their lack of toxicity for spirulina culture, the content of proteins in biomass was determined. Titanium nanoparticles applied in minimum concentrations of 0.5-15 mg/L did not alter protein synthesis, but a tendency to decrease with values 9-10% lower than in control samples was established. TiO2NP concentrations of 20-30 mg/L reduced the protein content in biomass by 17%. This result demonstrated the inert nature of titanium oxide nanoparticles, while the change in protein content in cyanobacterial biomass was insignificant. Based on the analysis of changes in the productivity of cyanobacterium Spirulina platensis, it can be stated the lack of toxic effect of TiO2NPs in the applied concentrations. The increase in the amount of spirulina biomass due to the action of TiO2 nanoparticles has led to a new field of their use – phycobiotechnology.