In this study, silver nanoparticles (AgNPs) were synthesized in an environmentally friendly manner using plant extracts from Luisia tristis. The formation of the nanoparticles was confirmed by a reddish-brown colour change and further characterized using ultraviolet–visible (UV–Vis), Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), and transmission electron microscope (TEM) techniques. The average size of the particles was found to be 16–48 nm. The antimicrobial activity of the AgNPs was evaluated against harmful bacteria and compared to the commonly used antibiotic ciprofloxacin. The AgNPs were found to be highly effective, with a 24 mm zone of inhibition against Escherichia coli, and more effective than ciprofloxacin. Additionally, a minimum inhibitory concentration assay was performed with a concentration of 100 mg/mL of AgNPs, which were found to effectively inhibit the growth of selected pathogens. Overall, the study demonstrates the potential for using plant-derived AgNPs as a natural and eco-friendly alternative for antimicrobial and antioxidant applications. This method is a fast, cost-effective way to generate silver nanoparticles at room temperature and may be useful in creating environmentally friendly antibacterial solutions for biomedical applications.