Biosynthesis of selenium nanoparticles (SeNPs) has gained great interest as a simple and eco-friendly alternative to conventional chemical methods. In this study, SeNPs were synthesized by using aqueous extract of marine Algae Turbinaria conoides. The formation of SeNPs using aqueous extract of Turbinaria conoides was confirmed visually by color change and their surface plasmon resonance peak at 270 nm, measured by UV-visible spectroscopy. Scanning electron microscopy was used to determine the size and form of the synthesised SeNPs. The synthesised SeNPs had an average size of about 76 nm and were almost spherical in form. The functional groups present in SeNPs was analysed by Fourier transform-infrared spectroscopy (FTIR). Antibacterial activity of SeNPs determined by an agar well diffusion assay demonstrated a significant activity against Escherichia coli,Staphylococcus aureus,  Pseudomonas aeruginosa and BTurbinaria conoides. acillus subtilus.Antioxidant activity of synthesized SeNPs determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay and 2,20-azinobis-3-ethylbenzothiazoline-6-sufonic acid scavenging assayrevealed efficient results. Our findings demonstrate that aqueous extract of Turbinaria conoides is an effective reducing agent for synthesis of SeNPs with efficient antibacterial and antioxidant activities.