The binodal data and liquid-liquid equilibrium of a 1-butyl-4-methylpyridinium tetrafluoroborate ([4-MBP][BF4]) + sodium chloride (NaCl) + H2O system were examined at T = 298.15, 303.15, 313.15, and 323.15 K. Moreover, the binodal curves were fitted to the Merchuk equation and another two four-fitting parameters empirical expressions, and the Othmer-Tobias, Bancroft and Setschenow-type equations were used to correlate the tie-line data. Good agreement was obtained between the experimental binodal data and the tie-line data. The results provide a theoretical basis for the extraction, separation, and purification of [4-MBP][BF4]-NaCl-H2O systems. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.