The major challenge in front of the agriculture sector is to provide food to an increasing population with good nutrients content without hampering the agroecosystem. About 40% of food wastages occur every year due to different crop diseases, pests, weeds, and insects. To overcome these problems, extensive use of chemical pesticides, fertilizers, and herbicides is common in the agriculture sector, which results in pollution of soil and water. The application of nanotechnology in the agricultural sector can provide modern tools for sustainable development without affecting ecosystems. Green nanomaterials further provide an eco-friendly route for the development of nanomaterials with economic advantages. Green nanomaterials from Au, Ag, Fe, Zn, TiO2, and silica, etc., have vast applications in the agriculture sector for nutrient enrichment and disease control in crops. Green nanomaterials are generally synthesized from different plant sources or microorganisms, which provide a sustainable route for applications. This review chapter presents an introduction to green nanomaterials from various biological sources, synthesis methods, and their characterization. Further, it discusses applications of green nanomaterials as nano biofertilizers, nano biopesticides, nano biosensors, carriers for nutrients, and other applications for sustainable agriculture.