In this work, the effect of two imidazolium-based ionic liquids with different anions, 1-butyl-3-methylimidazolium bromide, [BMIm]Br, and 1-butyl-3-methylimidazolium chloride, [BMIM]Cl, on thermodynamic properties of acetaminophen was investigated. For this purpose, measurement of density rho speed of sound it and specific electrical conductivity kappa for acetaminophen in aqueous solutions of ionic liquid was made at T = 293.15 to 308.15 K and at atmospheric pressure. The standard partial molar volumes V-phi(0), partial molar isentropic compressibility K-phi(0), hydration number n(H), and Hepler's constants (partial derivative V-2(phi)0/partial derivative T-2)(P) have been calculated from the density and speed of sound data. The limiting molar conductivities Lambda(0) and ion association constants K-A for the ionic liquids in aqueous solutions, of acetaminophen have been estimated using the low concentration chemical model (lcCM). The results confirm presence of a strong attractive interaction between acetaminophen molecules and the ionic liquids which that becomes stronger with increase in anion size.