Abstract Apparent molar volumes, V ∅ of amino acids i.e. glycine, l -alanine, l -serine, l -threonine and DL- α -aminobutyric acid in pure water and in aqueous solutions of imidazolium based ionic liquid, 1-butyl-3-methylimidazolium bromide, [ BMIm ] [ Br ] were determined from precise density measurements at temperatures T = (288.15–318.15) K and at atmospheric pressure. Partial molar volumes V 2 o and partial molar volumes of transfer, Δ tr V 2 o of amino acids in aqueous [ BMIm ] [ Br ] solutions have been obtained from the V ∅ data. The V 2 o values follow the order: l -threonine > DL- α -aminobutyric acid > l -serine > l -alanine > glycine. Positive Δ tr V 2 o values for all the studied amino acids indicate the dominance of hydrophilic-ionic interactions between amino acids and [ BMIm ] [ Br ] . The partial molar expansibilities ( ∂ V 2 o / ∂ T ) P and their second order derivatives ( ∂ 2 V 2 o / ∂ T 2 ) P , volumetric interaction parameters, V AB and V ABB , hydration number, n H have been calculated. The charged end groups, V 2 o ( NH 3 + , COO - ) , side chain contributions of the amino acids, V 2 o ( R ) and apparent specific volume, v ∅ have also been obtained from V 2 o and V ∅ data. The results have been interpreted in terms of possible molecular interactions.