<p>Polymer nanocomposites based on polyelectrolyte complexes of carboxymethyl cellulose (CMC)—chitosan of different molecular weights (low, medium, high) and Ag or Ag/Ag₂O nanoparticles were formed by reducing Ag⁺ ions in the polymer matrix using green tea, ginger or propolis extracts. The structural and morphological features, antimicrobial, antiviral and cytotoxic activity of the synthesized samples were investigated. It was found that when silver ions are reduced in polymer systems of CMC—Ag⁺—low molecular weight chitosan using green tea and ginger extract, Ag/Ag₂O nanoparticles are formed, while the use of propolis extract results in the formation of metallic silver nanoparticles. It was found that when using green tea extract, the smallest particles with an average size of ~ 11&#xa0;nm are formed, and when using ginger and propolis extracts, particles with an average size of ~ 20 and 44&#xa0;nm are formed, respectively. It was found that silver-containing nanocomposites based on CMC and low molecular weight chitosan exhibit antibacterial activity against microorganisms <i>S. aureus</i> and <i>E. coli</i> and antiviral activity against influenza A virus type (H1N1) and herpes simplex virus type 1. It was shown that the studied nanocomposites did not exhibit cytotoxic activity against MDCK and Vero cells. All undiluted and diluted samples reduce the proportion of live cells by no more than 28.5%.</p>