Densities and viscosities of the ternary system (ethanol + methylbenzene + 2-methyl-2-propanol) and its binary subsystems were measured at T = 298.15 and 318.15 K and atmospheric pressure. Densities were determined using a vibrating-tube densimeter. Viscosities were found with an automatic microviscometer based on the rolling ball principle. From the experimental data, the excess molar volumes (V-E) and deviations in viscosity (Delta eta) were derived. The binary V-E and Delta eta data were correlated with the RedlichKister equation. The ternary V-E and Delta eta data were fitted to the equation based on Cibulka and the equation of Singh et al., respectively. The values of V-E and Delta eta were used to discuss the nature of mixing behaviors for the mixtures, and leading to these excess values is perhaps due to the complex formation and/or accommodation between molecules. To describe the ternary system, several mixtures with specially designated concentrations of 2-methyl-2-propanol were considered.