Phyconanotechnology, which combines algae and nanotechnology, offers a viable approach to producing eco-friendly nanoparticles that can be used for several applications, including biomedical and environmental fields. This chapter provides an in-depth analysis of the potential of several types of algae as feedstocks for the synthesis of green nanoparticles. It examines their distinct features and the complex mechanisms involved in their biological creation. This chapter offers a comprehensive exploration of separation and characterization procedures, as well as several forms of nanoparticles formed from algae. It provides a detailed explanation of lipid-based, protein-coated, polysaccharide-encapsulated, and other new types of nanoparticles. The utilization of these algal-derived nanoscale particles and their application diverges in the field of medicine, promising systems for delivering drugs and as agents for both therapy and diagnosis. In the realm of agriculture, they play a role in the development of nano pesticides, fertilizers, and enhancements in crop productivity. Algae-based nanomaterials have significant ecological impact and sustainability, particularly in environmental remediation applications such as water and soil cleaning. The chapter explores the regulatory framework and safety concerns related to phyconanotechnology, while also discussing upcoming trends in the field. The discourse on the potential influence of this growing field is shaped by the integration of developing technologies, issues in sustainable manufacturing, and opportunities for commercialization. The chapter provides a thorough overview of recent advancements in phyconanotechnology, focusing on original information and providing insights into its intriguing domains.