Here the thermoresponsive self-assembly of diblock copolymers comprising poly(ethyl glycidyl ether) (PEGE) and poly(ethylene oxide) (PEO) in water and ionic liquids (ILs) is investigated. PEGE undergoes lower critical solution temperature (LCST) phase separation in both water and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide ([C(2)mim][NTf2]), while PEO is a compatible segment for these solvents. The diblock copolymers, PEGE-b-PEO, undergo thermosensitive unimer-micelle transitions at temperatures close to the LCST point (T-LCST) of the PEGE homopolymer in water but not in [C(2)mim][NTf2], even at temperatures much higher than T-LCST. The difference in the thermoresponsivity of these solutions is explored using differential scanning calorimetry results from rather small magnitudes of the thermodynamic parameters for the phase transition of the PEGE segment in [C(2)mim][NTf2], compared with those in water. Due to such small magnitudes, T-LCST of the PEGE segment for the block copolymers in the IL is greatly affected by the elongation of soluble PEO segments.