 This paper reports on the synthesis of silver nanoparticles using an aqueous extract of seaweed entremorpha compressa as a reducing and stabilizing agent. The resulting particles were characterized by Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and transmission electron microscopy. The particles exhibited spherical shapes with sizes ranging from 4 to 24 nanometers and were found to be highly crystalline. The particles were tested for antibacterial and anti-cancer activities, and it was found that they had strong antimicrobial and anti-cancer properties. Additionally, the particles were shown to reduce the viability of cancer cells, suggesting potential use in cancer therapy. This article was authored by Vijayan Sri Ramkumar, Aravalgam Pugazendi, Kumar Gopalakrishnan, and others.