An electrolyte for a lithium secondary battery, the electrolyte comprising: a lithium salt; an organic solvent; and an oligomer represented by Formula 1 or a polymer derived from the oligomer represented by Formula 1: wherein, in Formula 1, R 1 and R 2 are each independently an alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, R 3 and R 4 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, R 5 is hydrogen or an alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, R' is an aliphatic hydrocarbon group or an aromatic hydrocarbon group, the aliphatic hydrocarbon group of R' is selected from the group consisting of a cycloalkylene group having 4 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, a cycloalkenylene group having 4 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, and a heterocycloalkylene group having 2 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, the aromatic hydrocarbon group of R' is selected from the group consisting of an arylene group having 6 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms and a heteroarylene group having 2 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, z and x are the numbers of repeating units, z is an integer of 1 to 10, x is an integer of 1 to 15, and n is an integer of 1 to 3. a lithium salt; an organic solvent; and an oligomer represented by Formula 1 or a polymer derived from the oligomer represented by Formula 1: wherein, in Formula 1, R 1 and R 2 are each independently an alkylene group having 1 to 5 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, R 3 and R 4 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, R 5 is hydrogen or an alkyl group having 1 to 5 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, R' is an aliphatic hydrocarbon group or an aromatic hydrocarbon group, the aliphatic hydrocarbon group of R' is selected from the group consisting of a cycloalkylene group having 4 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, a cycloalkenylene group having 4 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, and a heterocycloalkylene group having 2 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, the aromatic hydrocarbon group of R' is selected from the group consisting of an arylene group having 6 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms and a heteroarylene group having 2 to 20 carbon atoms unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, z and x are the numbers of repeating units, z is an integer of 1 to 10, x is an integer of 1 to 15, and n is an integer of 1 to 3.