The ionic liquid 1-hexadecyl-3-methylimidazolium bromide ([C16MIm]Br) has been used as a novel cationic surfactant for separation of phenolic compounds, including quinol, phloroglucinol, resorcinol, phenol, p-cresol, and m-nitrophenol, by micellar electrokinetic capillary chromatography (MEKC). The effects of buffer concentration and pH, concentration of [C16MIm]Br, and applied potential were studied. Use of the optimized buffer (25 mmol L−1 NaH2PO4), 10 mmol L−1 [C16MIm]Br, and an applied potential of −15 kV enables optimum separation with regard to resolution and migration time. The phenolic compounds were detected at 214 nm. The micelle of this long-alkyl-chain imidazolium ionic liquid acts as a pseudo-stationary phase in this MEKC separation.