Synthesis of nanomaterials by biological approach is innovative, cheaper and environmental friendly and requires less-labor. In this regard, the present study focused on the synthesis of silver nanoparticles from the extract of Sargassum tenerrimum. Synthesized silver nanoparticles were well-characterized by UV-Visible Spectroscopy (UV-Vis), Fourier-Transform Infra-red Spectroscopy (FT-IR), Transmission Electron Microscopy analysis (TEM) and Dynamic Light Scattering (DLS). It was found that spherical shaped nanoparticles of size 20 nm were found in TEM analysis and showed effective anti-bacterial activity against standard reference strains. Altogether, extracts from seaweed were screened for phytochemicals followed by FT-IR prediction to reveal chemical functional groups present. The results showed that the anti-bacterial activity of silver nanoparticles was comparably higher than the phytochemicals present. Therefore, the present study elucidates silver nanoparticles can play a vital role in nano-based therapy in future.