In different fermentation processes the separation of the products from aqueous solution is an energy-intensive process step, particularly for hydrophilic products like diols. As an alternative to evaporation and distillation, liquid liquid extraction of these products is often limited by the unfavorable partition behavior of the diols. In this work phase equilibria for four quaternary systems consisting of water, 1,3-propanediol, a salt (K2HPO4, K2CO3, or Na2CO3), and a short-chain alcohol (ethanol, 1-propanol, or 2-propanol) were investigated. For all investigated systems favorable partitioning behavior of the hydrophilic diol into the organic phase was found. The partition ratio of the diol depends strongly on the salt content of the system. In the region of salt mass fractions in the salt-rich phase lower than 30 wt % highest partition ratios as well as highest selectivities were reached with systems of the type Na2CO3 + H2O + 1-propano1/2-propanol + water. Furthermore, the predictive thermodynamic model COSMO-RS was used with an electrolyte extension for the prediction of the partition ratio of the diol at infinite dilution in the 1,3-propanediol free systems. The partition ratio was overestimated by the model. Nevertheless, a qualitative agreement concerning the order of the partition ratio was reached at lower salt contents, and the increase in the partition coefficient with an increasing mass fraction of the salt was predicted for all systems except for the K2CO3 + H2O + ethanol system at high salt mass fractions.