The densities, rho, speeds of sound, u and refractive indices, n(D) of binary mixtures of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [Bmim][NTf2] and pyrrolidin-2-one, including those of pure liquids, over the entire composition range were measured at temperatures (298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K and atmospheric pressure. Using the experimental results, the excess molar volume, V-m(E), excess isentropic compressibility, kappa(E)(s), excess molar isentropic compressibility, K-s,m(E), excess speed of sound, u(E), deviations in refractive index, Delta(phi)n(D), deviations in molar refraction, DRM have been calculated. The partial molar volume and compressibility, excess partial molar volume and compressibility over the whole composition range; and the partial molar volume and compressibility, and excess partial molar volume and compressibility, of the components at infinite dilution have also been calculated. The excess properties were correlated by the Redlich-Kister polynomial equations. The variations of these parameters with composition and temperature are discussed in terms of intermolecular interactions prevailing in these mixtures. The V-m(E) values for these mixtures were also calculated by using Prigogine-Flory-Patterson (PFP) theory and the results are compared with experimental findings. (C) 2016 Elsevier Ltd.