Thermo-sensitive polymer-grafted carbon nanotubes were prepared by surface-initiated atom transfer radical polymerization and carefully characterized. A reversible, temperature-induced phase transfer behavior of these organic-inorganic hybrids between water (with a decrease in temperature to 20 °C) and a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim]NTf2) (with an increase in temperature to 90 °C), was observed. Mechanism analysis suggests that this reversible phase transfer between water and [Emim]NTf2 is due to the relative affinity of the two solvents for the poly(ethylene oxide) units grafted on the carbon nanotubes. Our results pave the way for further design of carbon nanotube-based, recyclable phase transfer vehicles as well as heterogeneous catalysts suited for a water-hydrophobic ionic liquid biphasic system.