Due to considerable impact on day-to-day life through superior functioning of energy, medicine, electronics, sensors and space industries young researchers are being attracted towards nanotechnology/biotechnology field. Selenium (Se) is acting as an essential element in most of the organism and beneficial nutrient in higher plants. Se nanostructures (NSs) i.e. nanospheres or particles (NPs) and nanowires (NWs) have unusual properties compared to their bulk counterparts. It has seven-fold lower toxicity than its other biologically utilizable materials. Several physical & chemical methods are being applied for the synthesis of Se NSs, but development of eco-friendly routes is of considerable importance towards biological applications. Recently microorganisms are being reported for the synthesis of Se NSs by reduction of oxyions in anaerobic and aerobic environments. This review briefly proposes the recent developments in the microbial synthesis, characterization, synthesis mechanism of Se NSs along with non-biological (solar, sensor, photocatalysis etc.) and biological (anticancer, antioxidant, antiprotozoal etc.) applications. Advantages of Se NSs synthesized using green approaches, over commonly used, are explored.