Nanotechnology shows revolutionary attempts to address humanity’s challenges, especially in addressing the severe disease burden of the world’s population. The use of conventional medicines is reported to be limited due to the development of antimicrobial resistance coupled with little research on new drug development, which continues to strain healthcare in contemporary times. However, using medicinal plants as remedies for diseases has increasingly garnered attention in research and is promising to combat the diseases that threaten human life. As a developing research area, researchers are exploiting the possibility of developing bio-nanoparticles from medicinal plants, which were earlier reported to possess therapeutic potential and enhance their effectiveness by incorporating a nanotechnology approach. Using medicinal plant extracts as reducing, capping, and stabilizing agents to prepare therapeutic metallic nanoparticles has shown promising results in advancing pharmaceutical nanotechnology. The plant-mediated nanoparticles exhibit enhanced drug delivery to the site of action, improved bioavailability, and better drug solubility. In this way, synthesizing bio-nanoparticles for therapeutic purposes provides a new approach to curbing the global disease burden emanating from antimicrobial resistance to conventional antibiotics and reducing millions of morbidities and mortalities. This chapter highlights an overview of nanoparticles and the different synthesizing methods, primarily focusing on African medicinal plants, their characterization, and their applications as therapeutic agents.