In this experimental work, nonlinear optical properties of Oxazine 720 laser dye in acetone, dimethyl sulfoxide, ethanol, and water were studied using z-scan method. It is found that the nonlinear behavior of Oxazine 720 dye in water is different from other organic solvents. The magnitude of nonlinear refractive index was obtained in the order of 10 -8 cm 2 /W and 10 -7 cm 2 /W for the 0.2 mM solutions of this dye in water and other solvents, respectively. Also, it was observed that in the aqueous solution reverse saturation absorption occurs while in other organic solvents, saturation absorption occurs and near the focal point of the lens, it is converted to reverse saturation absorption. These differences in the nonlinear refractive index and nonlinear absorption changes of aqueous solution and other solutions can be due to strong aggregative behavior of dye molecules in water.