Green synthesis of metal nanoparticles is an important technique in improved methods of eco-friendly nanoparticles production. In this investigation, the biomedically valid gold nanoparticle was synthesized by using marine brown algae Turbinaria conoides. The colour changes from brown to pinkish red confirmed the gold nanoparticles synthesis. The triangle, rectangle and square shaped and 60 nm average sized gold nanoparticles were observed by Scanning Electron Microscope (SEM). The nature of elemental gold was analysed by using Energy dispersive analysis (EDS). Finally the antibacterial activity of gold nanoparticles was performed; it shows Streptococcus sp having the maximum inhibition and medium range of inhibition was examined against Bacillus subtilis and Klebsiella pneumoniae.