Blossoming advancements and implementation of technologies in nanoscience have thrown open avenues for the nano-revolution which divulge the contribution of plants and microorganisms in bio and green synthesis of nanoparticles which seemed to have drawn indisputable attention of researchers towards this new area of research. Microalgae are often single-celled filamentous photosynthetic microorganisms or colony-forming microorganisms, contributing significantly to the biodiversity of the earth. Synthesis can be done in a simple aqueous medium at a normal pH level at ambient temperature and pressure since they are comparatively easy to handle, less hazardous, and less detrimental to the environment. However, many approaches based on physiochemical methods are being implemented for nanoparticle synthesis. As a result, there is an increasing need to find alternative, affordable, trustworthy, biocompatible, and environmentally acceptable ways for developing nanoparticles. Hence, biological approaches for reducing metals to corresponding nano-dimension particles are frequently used due to their environment-friendly, cost-effective, energy-effective, and lack of chemical contaminants for biological and medical applications. This chapter summarizes the fabrication of nanoparticles via different algal species because of their fascinating physical properties, distinguishing photoluminescence properties, biocompatibility, and active surface chemistry.