The aim of the study was to check the ability of microorganisms of Pseudomonas genus to form silver nanoparticles. Among the studied strains, Pseudomonas stutzeri showed the highest level of activity. Maximal amount of extracellular nanoparticles formation was observed after addition of 100 mg/l of silver ions. It is shown that the shape and size of the formed nanoparticles depends on the initial concentration of Ag+. Addition of the silver ions (in concentration 25-100 mg/l) to the bacterial culture medium leads to the appearance of the nanoparticles with the sizes varying from 20 nm to 300 nm which then form agglomerates, their sizes vary from 150 nm to 500 nm.