The viscosities and the densities of the ternary mixtures water + n-pentyl acetate + methanol and those of the constituent binaries have been measured at 303.15 K and atmospheric pressure in the homogeneous region. The respective viscosity deviations and excess molar volumes were fitted to a Redlich-Kister (RK) type equation. A modified Redlich-Kwong-Soave equation of state due to Fuller was used with the Eyring kinematic viscosity model to correlate viscosities of binary data. The equation of state constants were calculated using the van der Waals one-fluid mixing rules with the cross-parameters, a(ij), obtained with the classical and a two-parameter Redlich-Kister combining rules. The new model correlates the viscosity of the binaries with an average absolute deviation <2%. Using the binary interaction parameters obtained from the regression of viscosity data the ternary viscosity and the binary and ternary density were also successfully predicted with an average absolute deviation of the same order of magnitude.