Conventional separation methods such as distillation, ion exchange precipitation, and solvent extraction have competed for decades with the membrane processes which are fascinated by many researchers. Low energy expenditure, high removal yield, affordable costs, appropriate selectivity, passable productivity, ease of scaling, and environmentally friendly are accounted as the most important capabilities of the membrane processes which can be replaced with other separation technologies. Integration of membrane technology and nanotechnology has revolutionized the membranes, e.g., thin-film nanocomposite membranes and mixed matrix membranes. Combining polymeric composites with nanostructures thanks to enhancing electromagnetic properties, chemistry, morphology and physicochemical stability are assumed as promising choices for the membranes fabrication. Nanofillers like carbon nanotubes (CNTs), graphene oxides (GOs), metal organic frameworks (MOFs), and fullerenes are the most common nanofillers that have been enforced in the amendment of polymeric membranes successfully. This chapter illustrates a comprehensive review of various nanofillers including organic nanofillers and inorganic nanofillers. This present overview focuses on the applied nanofillers in polymeric composites to fabricate mixed matrix membranes, and thin-film nanocomposite membranes also show applications of the nanostructures in the membrane industry.