In this paper, the rheological behavior of MgO-Water nanofluid at different temperatures ranging from 25 degrees C to 60 degrees C and different volume fractions ranging from 0.07% to 1.25% has been examined. Suspensions were prepared by dispersing MgO nanoparticles in Water. Viscosities were measured at the different shear rate range of 6.115 s(-1) to 73.38 s(-1). Results showed that the base fluid exhibits Newtonian behavior and the nanofluid samples exhibit a non-Newtonian behavior. The obtained results also showed that the viscosity increases with an increase in the solid volume fraction of nanoparticles and decreases with increasing temperature. Finally, the findings were compared with famous models and it was found that these models can not able to explain this nanofluid behavior and doesn't have reasonably excellent agreement. (C) 2018 Elsevier B.V. All rights reserved.