Chemical fertilizers and pesticides are causing problems in our food system, leading to the degradation of agricultural land, crops, and human health. This justifies the urgent need to find natural alternatives. This chapter explores a promising green technology: algae-mediated nanoparticles, i.e., phyconanomaterials. These materials are much safer for the environment than traditional chemicals, as they are eco-friendly, less toxic, and sustainable. Properties like catalytic activities, high surface area, shape, and metal tolerance make these nanoparticles fit to be used in agriculture. Different types of algae, such as Ulva fasciata, Chlorella, and Spirulina are used to obtain silver, titanium oxide, and copper oxide nanoparticles. This chapter discusses the synthesis and applications of phyconanomaterials-based biofertilizers in farming, offering insights on phyconanomaterials on soil quality as well as plant growth and development.