•1-Butyl-3-methylimidazolium salicylate reduces the bitter taste and increases the solubility of caffeine in water.•The caffeine molecule in BmimSal aqueous solution is an anomalous structure-maker.•π-π interactions between caffeine and salicylate molecules occur at higher temperatures.•BMIM+ cation stabilize the salicylate anion enabling its more uniform position around the caffeine molecule. In this study, a detailed physicochemical characterization of caffeine in 0.1 mol∙kg−1 of 1-butyl-3-methylimidazolium salicylate (abbreviation BmimSal) aqueous solutions is performed based on density, speed of sound, refractive index and viscosity measurements in the temperature range from T = (293.15–313.15) K. BmimSal slightly increases the solubility of caffeine in water. Data obtained from the volumetric and viscosimetric measurements indicate that BmimSal promotes the self-aggregation of caffeine in water. Molecular dynamic simulations provided insight into how BmimSal increases caffeine solubility in water. At higher temperatures, the salicylate anion has stronger interactions with caffeine through π–π interactions than at lower temperatures.