Silver nanoparticles (AgNPs) are gaining a great deal of attention in biomedical applications due to their unique physicochemical properties. In this study, green synthesis of AgNPs was developed using seaweed polysaccharide fucoidan. The AgNPs were further coated with chitosan to form an electrolyte complex on the surface. The developed chitosan–fucoidan complex-coated AgNPs were characterized using UV-visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). FT-IR results suggested strong polyelectrolyte complexation between fucoidan and chitosan. The developed chitosan–fucoidan complex-coated AgNPs significantly inhibited microbial growth. Moreover, the AgNPs showed efficient anticancer activity in human cervical cancer cells (HeLa). This study demonstrated that chitosan–fucoidan complex-coated AgNPs hold high potential for food and cosmeceutical applications.