Abstract In this work, we report the densities, ρ and apparent molar volumes of imidazolium based ionic liquid (1-butyl-3-methylimidazolium bromide, [Bmim]Br) in water and in aqueous solutions of two pentoses namely d(−)-ribose (Rib) and d(−)-arabinose (Arb) at different temperatures (288.15 to 318.15) K and at atmospheric pressure. The infinite dilution partial molar volume, V2° and empirical parameters (Sv and Bv) were evaluated by using Redlich-Mayer type of equation. The volume of transfer (ΔtV2°) for [Bmim]Br from water to aqueous monosaccharide solutions were found to be positive and decrease in the following order: Rib > Arb. The Sv, Bv ΔtV2° and other parameters such as expansion coefficients and interaction coefficients were discussed in terms of interactions occurring between monosaccharides and ionic liquid. Modulation of volumetric properties of BmimBr in mixed aqueous solutions has also been discussed in relation to the stereochemistry of monosaccharides.