Densities and viscosities of binary liquid mixtures of diethyl malonate with isomeric xylenes were reported at (303.15, 308.15, 313.15 and 318.15 K). From the experimental data, deviation in Viscosity (Δη) and excess Gibbs free energy of activation of Viscous flow (ΔG*E) were evaluated. The deviations in viscosity and excess Gibbs free energy of activation of viscous flow were correlated with Redlich-Kister polynomial equation. Viscosity theories like Grunberg-Nissan, Katti-Chaudhri, Heric-Brewer, Hind et al. and McAllister four body models have been applied to correlate the viscosity of binary mixtures.