In this study aim was to perform green synthesis of synthesis silver nanoparticles (LAC-AgNPs, RAE-AgNPs and BAE-AgNPs) by using Desmodesmus sp., intracellular and extracellular synthesis methods and to compare the obtained products with physicochemical characterization techniques. The structural, morphological and optical properties of the synthesized nanoparticles were characterized using UV-Vis spectroscopy, TEM, SEM-EDS, FTIR, DLS and zeta potential. These results clearly show that silver nanoparticles (AgNPs) could be synthesized in different sizes and stabilities with various biological materials obtained from Desmodesmus sp. LAC-AgNPs had size of 10-30 nm, RAE-AgNPs had size of 4-8 nm and BAE-AgNPs had size of 3-6 nm. Also, the antibacterial activity of silver nanoparticles synthesized as intracellular and extracellular showed a strong antibacterial effect against pathogens such as Salmonella sp. and Listeria monocytogenes. Additionally, they have effective antifungal activity against Candida parapsilosis. The broth microdilution method was used for examining antibacterial antifungal effect of synthesis AgNPs. The minimum inhibitory concentration against Salmonella sp., Listeria monocytogenesis and Candida parapsilosis were recorded as 3,125 mu l, 1,5625 mu l and 0,78125 mu l synthesis AgNPs, respectively. As a result, it has thought that different sizes of synthesis AgNPs may have a great potential for biomedical applications.