The density and viscosity of binary ionic liquid mixtures with a common anion, 1-ethyl-3-methylimidazolium tetrafluoroborate + 1-propyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate + 1-propyl-3-methylimidazolium tetrafluoroborate, and 1-propyl-3-methylimidazolium tetrafluoroborate + 1-hexyl-3-methylimidazolium tetrafluoroborate were determined in the temperature range of (298.15 to 343.15) K. The excess molar volumes were calculated and correlated by Redlich-Kister polynomial expansions. The viscosities for pure ionic liquids were analyzed by means of the Vogel-Tammann-Fulcher equation, and ideal mixing rules were applied for the mixtures.