Oligosaccharides are low molecular weight carbohydrates, containing sugar moieties with degree of polymerization (DP) between 3 and 10. The nondigestible oligosaccharides are resistant to human digestive enzymes viz., salivary and pancreatic amylases (Weijers and others 2008). Thus, they pass through the upper digestive system intact and get fermented in the lower colon, producing short-chain fatty acids (SCFAs), which, in turn, nourish the resident beneficial microbiota (Mussatto and Mancilha 2007; Morris and Morris 2012). Most of the prebiotics identified till date are nondigestible oligosaccharides (Wang 2009; Saad and others 2013). Since their recognition as important food additives in 1980s, these functional oligosaccharides have gained phenomenal popularity (Saad and others 2013). Their health benefits graduated them to nutraceutical league with ever increasing market share. The U.S. market for prebiotic ingredients is currently estimated at metric tons and million dollars, which is predicted to double in the next 5 y to more than U.S. $220 million, according to market researcher Frost and Sullivan. The Transparency Market Research observes that the prebiotics demand was worth USD 2.3 billion in 2012 and is expected to reach U.S. $4.5 billion by 2018. The stability of oligosaccharides depends on the sugar residue content, anomeric configuration, and linkage types (Raman and others 2005). The functional oligosaccharides include lactulose, fructo-oligosaccharides (FOSs), galacto-oligosaccharides (GOSs), soybean oligosaccharides (SOs), lactosucrose, isomalto-oligosaccharides (IMOs), gluco-oligosaccharides (GLOSs), xylo-oligosaccharides (XOSs), gentio-oligosaccharides (GeOSs) arabinoxylan oligosaccharide (AXOS), mannan oligosaccharides (MOSs), pectin-derived acidic oligosaccharides (pAOSs), chito-oligosaccharide (COS), agaro-oligosaccharide (AOS), human milk oligosaccharide (HMO), cyclodextrins (Patel and Goyal 2011), xanthan-derived oligosaccharides (XDOs) (Wu and others 2013a), and alginate-derived oligosaccharide (ADO) (He and others 2013). Oligosaccharide research is an area of intense investigation, for its multitude of biological potencies. Several reviews have been published in recent times, but they are not holistic, rather they deal with individual oligosaccharides. Sangwan and others (2011) summarized the role of GOS; Costa and others (2012) demonstrated that the importance of FOS and Bertino and others (2012) have reviewed the biological functions of HMO. Raman and others (2013) elaborated the significance of tailor-made prebiotics, probiotics, and synbiotics in colorectal cancer management owing to their antimutagenic activity. On the other hand, this manuscript deals with most of the existing functional oligosaccharides, and their food and pharmaceutical applications. The authors had published a review article on “functional oligosaccharides” in a reputed journal in 2011 (Patel and Goyal 2011). Since then, several key developments have occurred in this area. This manuscript furnishes an account of those key findings. Therefore, an attempt has been made in the following text to dovetail the enormous information available on the various aspects of oligosaccharides as prebiotics.