Phase diagrams and densities of an aqueous two phase system containing polyethylene glycol (PEG) 4000, triammonium citrate, and water were determined at different temperatures. The effect of temperature on densities of aqueous PEG 4000 and aqueous triammonium citrate were determined at (25, 30, 35, 40, and 45) degrees C. The densities of the PEG 4000 + triammonium citrate + water system were determined at (25, 35, and 45) degrees C. The density increases with an increase in PEG concentrations and reduces with an increase in temperature. Binodal curves, phase equilibrium compositions, tie-line lengths (TLL), slopes of the tie-line (STL), density differences, and effective excluded volumes (EEV) for the above aqueous two phase system were determined at different temperatures (25, 35, and 45) degrees C. Binodal curve data were fitted with available literature correlations, and the constants were reported. The effective excluded volumes (EEV) were calculated from binodal curve data for different temperatures. The salting out efficiency is greater at higher temperature as the EEV is larger at higher temperature. The effect of tie-line length (TLL) on the density difference exhibited between the two phases was evaluated. The experimental tie-line compositions were related with Othmer-Tobias and Bancroft equations, and linear dependency was confirmed.