This work concerns the obtained results by the thermodynamic investigation of the (NaCl + serine +water) electrolyte system based on the experimental potentiometric data. The potentiometric measurements were performed on the galvanic cells without liquid junction of the type: AglAgClINaCI (m), serine (wt%), H2O (1 wt%)I Na-ISE, in various mixed solvent system containing 0, 2, 4, 6, 8 and 10 mass fractions (%) of serine over ionic strength ranging from 0.0435 to 3.4999 mol kg(-1) at T= (298.2 and 303.2)K. The modeling of this system was made based on the extended Debye Hiickel equation, Pitzer and Pitzer-Simonson-Clegg models. The obtained parameters were used to calculate the values of the mean activity coefficients of NaCI, the osmotic coefficients, and the excess Gibbs-free energies based on Pitzer model for the investigated system. Also, the mean activity coefficients of NaClbased on mole fractions and excess Gibbs free energies were determined in according to Pitzer-Simonson-Clegg model. (C) 2014 Elsevier B.V. All rights reserved.