At present, silver nanoparticles (AgNPs) are used in numerous technologies and are being incorporated into a wide range of consumer products, which are based on optical, conductive and antibacterial properties of these nanoparticles. An obvious area is AgNPs applications in molecular diagnostics as biosensors and numerous tests, where nanostructured materials can be used as biological markers for quantitative detecting. An important aspect of applying AgNPs is based on their activity as biosensors and regulators of plant metabolism. Due to the fact that it does not require organic media, technologies involving photosynthetic organisms are far less expensive. Biological effect of silver nanoparticles in particular upon microalgal and cyanobacterial metabolism is poorly studied. For these reasons, the study of the effect of AgNPs on biosynthesis of biologically active compounds by cyanobacteria and microalgae and the ways of enhancing the yield of this process is a perspective field of nanobiotechnology. In our study, 5 nm size AgNPs were used to cultivate cyanobacterium Spirulina platensis. It was determined the beneficial effect of these nanoparticles on spirulina growth through enhanced productivity by about 22-30%. Maximum biomass content of 1.13 g/L was obtained in the presence of these nanoparticles in 1:5 dilution, which was 30% more. The process of protein biosynthesis was virtually unaffected by the presence of AgNPs. Thus, the protein content oscillated in biomass within the limits of protein content characteristic of this strain. A similar picture was also characteristic for polysaccharides. These functional compounds were relatively inert to AgNPs presence. As in the case of proteins, polysaccharide content remained in the area of characteristic values for this spirulina strain. Another situation was lipid dynamics in spirulina grown in the presence of AgNPs. Lipid content was lower by about 16% at concentration of 0.5 mM of AgNPs, and had an increasing trend at dilutions of 1:5, 1:10 and 1:20 of this AgNPs concentration. An increase in lipid content with about 52% was produced in spirulina biomass at 1:1 dilution of AgNPs. Therefore, AgNPs exhibit a varied biological effect on the productivity and content of biologically active compounds from Spirulina platensis. Namely, an effect from stimulative (productivity and lipids) to adaptogenic one: it does not change protein and polysaccharide content. Since the levels of compounds from spirulina grown in the presence of AgNPs are comparable to those characteristic of this culture, obtained biomass could be used as raw material for nutraceuticals.