We have reported an eco-friendly process for the synthesis of stable silver nanoparticles from Rhizophora apiculata. The absorption maximum of silver nanoparticles as characterized by UV-Visible spectrophotometer was found to be around 422 nm. The transmission electron microscopy study revealed the presence of spherical shaped nanoparticles with an average size of 15 nm. The antibacterial activity of gentamicin and chloramphenicol increased in the presence of AgNPs against the test strains. The research provides an important direction in the development of new antimicrobial agents.