The ionicity of ionic liquids (IL) is related to the ionic nature of these fluids and is a useful indicator of the characteristic properties of a given ionic liquid. In this work, we studied the effects caused by the addition of different inorganic salts (IS), on the ionicity of the ionic liquid 1-ethyl-3-methylimidazolium acetate. The solubility of different inorganic salts, based on the ammonium and the sodium cations, in this IL at room temperature was experimentally determined. Thermophysical properties, such as viscosity, density, conductivity, and refractive indexes, of the 1-ethyl-3-methylimidazolium acetate + inorganic salt mixtures were measured in different concentrations of IS, and the ionicity of the systems was calculated. The results showed that when ammonium-based salts are used, the ionicity of the ionic liquid can be increased, leading to the formation of high ionicity ionic liquids.