Plants are the natural factories for nanoparticle production as many of their products are being used for metallic nanoparticles production. Silver nanoparticles are being used in a number of consumer products, remediation processes, and medicines due to their antimicrobial and anti-inflammatory and catalytic activities. Present work focuses on a simple, one-step, environmental-friendly biosynthesis of silver nanoparticles using silver nitrate as precursor and leaf extract of herb species (Sida acuta); a common wireweed of Malvaceae family, which acts as reducing as well as capping agent. Synthesized nanoparticles were characterized for their morphological description using different techniques like UV-Vis spectroscopy, dynamic light scattering (DLS), transmission electron microscope (TEM) and Fourier transform infra-red (FT-IR) spectroscopy. The antimicrobial activity of these nanoparticles was studied against Pseudomonas aeruginosa and Candida albicans. The results showed good inhibitory effect against Pseudomonas aeruginosa and Candida albicans and found to exhibit good antibacterial activity especially at lower concentrations of 4 μg/ml and 8 μg/ml.