Nanotechnology has revolutionized the agricultural sector by promising sustainable agriculture through providing nanofertilizers, nanopesticides, nano-antimicrobials, stress smart crops, bioremediation, increased crop yield, and plant growth. Nanoparticles synthesized from plant growth promoting algae (phyco-nanotechnology) via biological route is anovel, developing, interesting field of nanotechnology which offers nontoxic, simple, affordable and eco-safe method of nanoparticle synthesis. Algae are economically and ecologically important, largest, diverse group of photoautotrophic organisms. Several species of micro and macro algae equipped with extensive variety of secondary metabolites, pigments, and proteins function as nano-biofactories for nanoparticle synthesis. Phycogenic nanoparticles have promising applications in agricultural sector and the present work highlights the synthesis of nanoparticles from various species of algae and the role of algal-based nanoparticles in sustainable agriculture.