Algae and their metabolites are possessing variety of properties that enhance different medical, industrial and environmental fields. These organisms are distributed in nature and adapt to variety circumstances. Nanotechnology is a fast developmental scientific field that a huge number of researches have globally published in order to cover its applications and provide recent findings of this significantly important field. This paper display back ground on nanotechnology, definition and historical overview, as well as different techniques involving the use of algae to facilitate the production of nano materials. Focusing on three groups; brown(phaeophyta), red (rhodophyta) and blue green algae (cyanophyta) and their extracellular metabolites. In addition, several medical applications of algae based nanomaterials is discussed. Including the use of these nano-sized particles against bacteria, virus, biofilm producing microbes and bio sensing technique.