The densities and refractive indices of binary mixtures containing 1-butyl-3-methylimidazolium tetrafluoroborate with water and monoethanolamine are measured at a temperature range of (293.15 to 353.15) K and within the whole range of composition. Excess molar volumes are deduced from the measured physical properties and correlated using Redlich-Kister polynomial equations. The excess molar volumes are positive for the entire mole fraction range, and the details are discussed. The thermal expansion coefficients are also derived from the measured density values. © 2011 American Chemical Society.