The versatile features of pure ionic liquids (ILs) can be considerably fine-tuned through mixing with suitable cosolvents, thereby expanding their role as potential green solvents to replace the traditional volatile organic solvents in several industrial processes. In the present work, the excess molar volume (V-m(E)), excess molar isentropic compressibility (K-s,m(E)), and deviation in refractive index (Delta D-n(phi)) have been determined from the measurement of density (rho), speed of sound (u), and refractive index (n(D)) by mixing imidazolium-based ILs: 1-methyl-3-alkyl imidazolium tetraflouroborate (alkyl = butyl, hexyl, and octyl) with aniline (AN) over an entire range of compositions and at temperatures ranging from 293.15 to 323.15 K at 5 K intervals and at atmospheric pressure. The magnitude of the negative V-m(E) and K(s,m)(E )increases absolutely as the temperature increases. Ion-dipole interactions and structural factors of the components of the mixture were held responsible for their nonideal behavior and have been interpreted. The influence of the alkyl chain of ILs and temperature on the thermophysical properties of the mixtures had been studied. We have predicted refractive indices for the studied binary mixtures using several mixing rules and compared the experimental values with them through standard deviation. We further compared our excess molar volume calculated through experimental density values with the predicted values using Prigogine-Flory-Patterson theory and Extended Real Association Model.