In this work, some new dual functionalized imidazolium-based ionic liquids 3-(3-butyl-1H-imidazol-3-ium-1-yl)propanenitrile chloride C 2CNBim Cl, 3-(3-allyl-1H-imidazol-3-ium-1-yl)propanenitrile chloride C 2CNAimCl, 3-3-(2-hydroxyethyl)-1H-imidazol-3-ium-1-yl propanenitrile chloride C 2CNHEimCl, and 3-(3-benzyl-1H-imidazol-3- ium-1-yl)propanenitrile chloride C 2CNBzimCl have been synthesized and characterized by 1H NMR, FTIR, and elemental analysis. Their thermophysical properties such as viscosity and density were measured for a temperature range of (293.15 to 353.15) K at atmospheric pressure, and their refractive indices were measured in the range of (293.15 to 333.15) K. The effect of functionalized side chains on their thermophysical properties was studied. The thermal expansion coefficient values were calculated using experimental density values. Thermal behavior of these ionic liquids was investigated using a thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC). © 2012 American Chemical Society.