Rheological properties are presented based on the flow behavior and the deformation of a substanceby the action of stress.Among the juices, watermelon is very popular and also verynutritious. In this research, the flow behavior of watermelonjuice was determined at concentrations of 40, 50 and 60 0Brix and temperatures of 15, 20 and 30 °C.Shear stress data obtained from juices were fitted with rheological models including Newtonian, power law. Also, concentration relationand temperaturewas determined by Arnius model and exponential law models.Based on the results obtained, both temperature and concentration decreased nvaluesbutincreased Kvalues.The power law model was also able to predict the dependence on apparent viscosity with concentration with high precision.The combined Arnius-power law model showed a high compliance for the effect of concentration-temperature on the apparent viscosity. Itcan be concluded that the temperature and concentration completely affect the rheological properties of Iranian watermelon juices.