The application of horizontal drilling and hydraulic fracturing stimulations for improving hydrocarbon productivity from low-permeable reservoirs is a well-established practice. However, the development of fracturing fluids that can maintain excellent rheological properties at reservoir conditions, as well as, minimize damage to the formation is still very challenging. There has been increasing interest in recent years in the improvement of the hydraulic fracturing stimulation through the application of nanotechnology. We review the current status of nanoparticles applications for hydraulic fracturing treatments of the unconventional reservoirs, highlighting the mechanisms and applications, the findings, the technical challenges and directions for future studies. The review literature demonstrated the promising applications of nanomaterials for improving the rheology of viscoelastic surfactant fluid, foam-based fluid and polymer-based fracturing fluid using nano-crosslinker and bio-polymer nano-composite. Results of previous studies showed that the unique properties of nano-materials, such as their smaller sizes, high specific surface area, magnetic properties, superior strength and stability could be exploited in the development of downhole nano-sensors, nano-proppants, gel breakers and fluid loss control agents. More work will be required to understand the cross-linking mechanisms of nano-crosslinkers and the mechanisms governing the enhancement in fracturing fluid viscosity in presence of nanoparticles at reservoir conditions. The potential applications of generally used nanoparticles such as, aluminum oxide (Al2O3), Copper oxide (CuO), carbon nanotubes and low cost nanoparticles such as calcium carbonate (CaCO3), silicon dioxide (SiO2) and fly-ash nanoparticles in unconventional reservoirs need to be further researched. Moreover, more emphasize should be place on nanoparticles performance at reservoir conditions, influence of nanoparticles agglomeration, economic feasibility, as well as environmental and health hazards of nanoparticles applications. The improved hydrocarbon recovery from the unconventional reservoirs through wettability alterations and interfacial tension reduction by nanofluids, and the use of nanoparticles-enhanced combined fracturing fluid systems present exciting future opportunities. © 2019 Elsevier B.V.