The use of the N-butylpyridinium tetrafluoroborate ([bpy] [BF4]) + N-butylpyridinium bis(trifluoromethylsulfonyl)imide abpy][Tf2N]) binary ionic liquid mixture as an aromatic extraction solvent has recently been proposed. To establish the potential of this mixture to be applied in an aromatic separation process, its physical properties must be measured. In this work, refractive indices, densities, and viscosities of this binary ionic liquid mixture have been determined over the temperature range from (303.15 to 353.15) K at atmospheric pressure. A comparison between the physical properties of the sulfolane and the properties gathered in this work has also been performed. The Bingham mixing rule has successfully estimated the viscosities of the IL mixtures from viscosity data of pure ILs. The accuracy of the group contribution method proposed by Ye and Shreeve and extended by Gardas and Coutinho in predicting densities of pyridinium-based IL mixtures has been studied. Refractive index deviations, excess molar volumes, and viscosity deviations have been correctly fitted to Redlich-Kister polynomial equations.