This study reports on the biosynthesis of Silver nanoparticles (AgNPs) using aqueous extract of neem root. The synthesis was carried out by mixing 1mM silver nitrate with the aqueous extract of neem root (10:1) under ambient conditions. Characterization was done by UV- vis spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, and Scanning Electron Microscopy (SEM). The antibacterial and algicidal activities of bio-synthesized AgNPs were investigated against some clinical bacterial isolates and a bloom forming cyanobacterial strain, respectively. Their potential application as an antimicrobial detergent additive was evaluated. The bio-synthesized AgNPs displayed maximum absorbance at wavelength 425 nm. The particles are predominantly spherical in shape with size ranging from 20 to 60 nm. Data obtained from FTIR indicate that the protein molecules in extract played a very active role in the reduction of silver ions to form AgNPs. The particles demonstrated considerable antibacterial activities against clinical isolates of Escherichia coli, Streptococcus sp, and Klebsiella pneumoniae as they induced inhibition zone of 12-23 mm. The algicidal activity displayed by the particles against the bloom forming cyanobacterial strain was appreciable. Similarly, the incorporation of AgNPs as additive in the locally made detergent led to the total inhibition of growth of Escherichia coli, Klebsiella pneumoniae, Candida sp, and Aspergillus flavus. Therefore, results obtained in this study suggest the promising applications of the particles as an antimicrobial agent in the water treatment and drug development. The particles exhibited potential application as an antimicrobial additive in detergent production.