Liquid-liquid interfacial tension of four 1-alkyl-3-methylimidazolium ([Cn-mim], n = 5, 6, 7, 8) based ionic liquids (ILs) and two n-alkanes (n = 6, 7) are reported in the temperature range from (283.15 to 343.15) K at atmospheric pressure using the platinum ring method. The interfacial tensions show a linear decrease with increasing temperature. The obtained data were correlated by an empirical equation, and fitting interfacial tension parameters are presented.