The effect of sodium bromide and potassium bromide on the liquid-liquid equilibrium (LLE) of the water + dimethyl sulfoxide + 1-pentanol system has been investigated at temperatures from (283.15 to 323.15) K under atmospheric pressure. The experimental results of the two quaternary systems (salt-containing) and the original ternary system (salt-free) show that the salt effect could be evaluated. The influence of sodium bromide is slightly more significant than that of potassium bromide. The compositions of the conjugated phases were correlated with the three-contribution electrolyte-NRTL model. In general, the model reproduces reasonably the LLE phase diagrams.