Silver nanoparticles were synthesized using arabinogalactan and sodium dioctyl sulfosuccinate to reduce and stabilize them. The average hydrodynamic size of the nanoparticles, determined by photon correlation spectroscopy, was 30 nm, and the zeta potential was –34.04 ± 1.54 mV. According to the electron diffraction method, silver in the sol sample is in metallic form. The preparation of silver nanoparticles showed antibacterial activity against opportunistic Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis and B. coagulans) bacteria. Silver nanoparticles also had antifungal activity against strains of phytopathogenic fungi of the genus Fusarium sporotrichioides and F. solani. A study of the cytotoxic activity of silver nanoparticles was made on human hepatoma cells of the HepG2 line. The inhibitory effect of silver nanoparticles on the metabolic activity and viability of tumor cells has been demonstrated. The average relative EC50 values for silver nanoparticles were 1.5 ± 0.4 μg/ml and 41.2 ± 3.9 μg/mL. The preparation of stabilized silver nanoparticles can find application in medicine, as a potential antimicrobial and antitumor agent, as well as in agriculture as a means of suppressing growth of phytopathogenic fungi.