The density and refractive index studies have been carried out for glycylglycine-FeCl2 in aqueous ethanol mixtures at four different temperatures in the range T = (288.15 to 318.15) K. A comparative study of the refractive indices obtained experimentally and those calculated by means of Gladstone-Dale and Lorentz-Lorenz relation has been made. Among them, the Gladstone-Dale equation afforded similar values to those obtained experimentally. Isentropic compressibilities, kappa(S), and excess molar isentropic compressibilities, K-S,m(E) were estimated using the Kirkwood model. Using the Redlich-Kister type equations, excess partial molar isentropic compressibilities, K-S,i(E), were also obtained. The observed negative values of K-S,2(E) in the water-rich region are due to the structural disorderliness. As infinitely dilute water is hydrogen-bonded to ethanol and glycylglycine, the variation of strength of interaction is not sensed by K-S,1(E,infinity).