As a “green” method for the synthesis of gold nanoparticles (AuNPs) plant extracts can be used instead of synthtic reagents. Thus, the use of natural flavonoids, alkaloids and phenolics as reducing and stabilizing agents is preferable to toxic chemicals. The synthesis process consists of reduction, nucleation and stabilization, and the size and shape of the nanoparticles influenced by pH, temperature and extract concentration. Many plants such as neem, tulsi and aloe vera have been found to be effective in the production of biocompatible AuNPs, which have found application in biomedicine, catalysis, and environmental monitoring and remediation. Reaction conditions are optimized to improve nanoparticle stability and functionality. Plant cell fermentation enhances control over the synthesis process and reduces the impact on the environment. Despite the problems of standardization and industrialization, plant-mediated synthesis of nanoparticles is a sustainable approach. This chapter highlights the mechanisms, advantages, and possibilities of plant-based AuNP synthesis in advancing green chemistry, precision medicine, and environmental friendliness.