An air- and water-stable hydrophobic ionic liquid N-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide ([c(4)3mpy][NTf2]) was synthesized and characterized. Density, surface tension, dynamic viscosity, and electrical conductivity of the IL were measured and calculated from (278.15 to 353.15) K. The glass transition temperature and decomposition temperature were determined by the differential scanning calorimetry and thermogravimatric analysis. The physicochemical properties like molecular volume, standard molar entropy, lattice energy, parachor, molar enthalpy of vaporization, interstice volume, thermal expansion coefficient, interstice fraction, etc. of the IL were estimated by the reported empirical and semiempirical equations. The dynamic viscosity and electrical conductivity data of the IL were described by Vogel-Fulcher-Tamman and Arrhenius equations, respectively. Then, the relationship between the molar conductivity and dynamic viscosity of this IL was expressed through the Walden rule.