Eutectic solvents (ESs) are a relatively new class of solvents that have been arousing a lot of attention due to their easy preparation and great tunability of their thermophysical properties, which has been granting their application in a wide range of areas. The aim of this work is to present a new ES based on the mixture of an organic sodium salt, sodium hexanoate and dodecanoate, and a long alkyl chain carboxylic acid, octanoic, nonanoic, and decanoic acids, and to infer about the effect of introducing a sodium atom. The solid-liquid phase diagrams of these new sodium salt-based ES were determined to evaluate the liquid window where they can be confidently used as solvents. Other important properties of solvents have also been studied, and in particular, density and viscosity, at atmospheric pressure and in the temperature range between 293.15 and 353.15 K, were measured. In addition, the polarity of these new sodium salt-based deep eutectic solvents (DESs) was evaluated in terms of the Kamlet-Taft α, β, and π* andETN parameters. The obtained results were compared with those of other commonly used hydrophilic and hydrophobic DESs and conclusions were taken.