For the biosynthesis of silver nanoparticles, various biological agents are used, including bacteria, cyanobacteria, fungi, yeast, algae and plants. When microorganisms are employed for the biosynthesis of silver nanoparticles, both intracellular and extracellular synthesis pathways are possible. Additionally, the synthesis of nanoparticles using exo- and endogenous cellular metabolites is feasible. Extracts from algae and plant containing polysaccharides, phenolic compounds, proteins, vitamins, carotenoids, astaxanthins, polyols, terpenoids, and sterol are used for the biosynthesis of silver nanoparticles. The mechanisms of nanoparticles biosynthesis using plant are not fully elucidated at present. However, it is known that hydroxyl, methylene, and carboxyl groups of various biological substances participate in the processes of silver ion reduction, nanoparticles formation, and stabilization. Depending on the biological agent and the biosynthesis method, nanoparticles of various shapes (spherical, cubic, icosahedral, triangular, pentagonal, hexagonal) and sizes are formed, affecting their biological properties. Biogenic silver nanoparticles exhibit antibacterial activity against both gram-negative and gram-positive bacteria. The mechanism of their antimicrobial action involves denaturation of bacterial surface proteins and inhibition of cell metabolism and respiration by damaging the electron transport system. Additionally, nanoparticles inhibit bacterial protein translation. Antitumor potential of biogenic nanoparticles has been observed in various cancer cell lines, though their selectivity towards cancer cells over normal cells has not been conclusively demonstrated. The antitumor effect of biosynthesized nanoparticles is associated with inducing cellular and subcellular morphological changes, enhancing oxidative stress and metabolic toxicity, and inducing apoptosis in cancer cells by reducing the expression of anti-apoptotic proteins and increasing the expression of apoptotic proteins.