Solvation properties of aspirin in nonaqueous ionic liquid solutions are of importance in pharmaceutical point of view. The effect of an ionic liquid on the thermodynamic properties of this drug in acetonitrile solutions has been investigated. The thermophysical properties including densities, viscosities, speeds of sound, and refractive indices for systems containing aspirin (ASA), ionic liquid {1-butyl-3-methylimidazolium bromide ([BMIm]Br)}, and acetonitrile (MeCN) have been measured at T = (288.15 to 318.15) K and atmospheric pressure. The measured data have been used to calculate the standard partial molar volumes V-phi(0), apparent molar isentropic compressibility kappa(0)(phi), molar refractions R-D, and viscosity B coefficients. The calculated Heplers constants (partial derivative V-2(phi)0/partial derivative T-2)(P) indicate that the ionic liquid behaves as a structure-maker in the studied solutions. The transfer volumes Delta V-t(phi)0 show that dominant interactions between aspirin and ionic liquid are ionpolar and polarpolar interactions. The results have been interpreted in terms of solutesolvent interactions.