Nanotechnology is a new technology, which has potential in food industry and agriculture. The product of nanotechnology is called nanoparticles. Nanoparticles have a diameter between 1 – 100 nanometer. One of the ways to produce nanoparticles is by biological method. Green synthesis is proved to produce non - toxic nanoparticles due to its phytochemicals. The phytochemicals including phenolic and flavonoid act as the natural reducing and stabilizing agent to synthesize silver nanoparticles (AgNPs). Guava (Psidium guajava L.) is known as a plant that is rich in polyphenols and phytochemicals, including tannins, carotenoids, phenols, flavonoids, and lectins that will act as green synthesis of AgNPs. The aim of this research was to study the green synthesis of AgNPs from leaves and fruits extract of guava. Different solvent polarities were used to extract dried guava leaves and fruits. Leaves that extracted with 50% ethanol have highest yield of AgNPs (146.996.07%) and highest antioxidant activity (80.806.46 mg AgNPs) resulted with size approximately 92. 5 nm. AgNPs were also treated with calcination process since it has the potency to increase the antioxidant activity. However, the calcination process at 100C, 300C, and 500C showed to lower the antioxidant activity of AgNPs compared to non – calcinated AgNPs