The reduction of silver metal through the headway of nanotechnology results in the production of silver nanoparticle (AgNP). It is an apparent metallic nanoparticle widely recognized in nanotechnology for its application in various platforms. Physical, chemical and biological methods have been studied and developed in the past decade to synthesize crystalline AgNP. Among these three, biological synthesis known as green synthesis has been extensively accepted as the most eco-accommodating and an efficient technique for the production of AgNP. Biological method consumes bio-reducing agents present in the bio-extract used for the synthesis of AgNP, such as microorganisms (bacteria and fungi) and plants. Extract from the part of the plant such as, stem, leaf, flower and bark is utilized as bioreducing agent, where its extractions ready to incorporate AgNP. Besides, bioreducing agents/stabilizing agents, commonly known as capping agents present in the biological extraction for the green synthesis of AgNP omits the consumption of additional chemical agents. The size and structure of AgNP from biosynthesis could be portrayed by electron microscopes and structural analysis. In the present chapter, the biosynthesized AgNPs from various biological extractions were presented with their significant application as antimicrobial agent. © 2019, Springer Nature Singapore Pte Ltd 2019.