A modified conjugated diene-based polymer comprising: a functional group derived from a modification polymerization initiator at one terminal, wherein the modification polymerization initiator comprises a derived unit from a compound represented by Formula 1, and a functional group derived from a modifier represented by Formula 2 at the other terminal: Wherein in Formula 1, R 1 is a hydrogen atom or a monovalent hydrocarbon group of 1 to 20 carbon atoms, R 2 is a divalent hydrocarbon group of 1 to 20 carbon atoms, which is unsubstituted or substituted with one or more substituents selected from the group consisting of an alkyl group of 1 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, and an aryl group of 6 to 30 carbon atoms, R 3 and R 4 are each independently a monovalent hydrocarbon group of 1 to 20 carbon atoms, which is unsubstituted or substituted with one or more substituents selected from the group consisting of an alkyl group of 1 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, and an aryl group of 6 to 30 carbon atoms, and X is S or O, wherein in Formula 2, R 5 and R 6 are each independently a monovalent hydrocarbon group of 1 to 30 carbon atoms or a glycol unit represented by wherein at least one of R 5 and R 6 is the glycol unit, R 7 is a single bond or a divalent hydrocarbon group of 1 to 30 carbon atoms, R 8 to R 11 are each independently a monovalent hydrocarbon group of 1 to 30 carbon atoms, R 12 is a divalent hydrocarbon group of 1 to 10 carbon atoms, j and k are each independently 0 or 1, and n is an integer of 1 to 10, wherein if R 5 is the glycol unit, 3-i-l and i are each independently 1 or 2 but are not 2 at the same time, and l is 0 or 1, if R 6 is the glycol unit, i and 1 are each independently 1 or 2 but are not 2 at the same time, and 3-i-1 is 0 or 1, and if both R 5 and R 6 are the glycol units, i is 1 or 2, and l and 3-i-l are each independently 0 or 1 but are not 0 at the same time. a functional group derived from a modification polymerization initiator at one terminal, wherein the modification polymerization initiator comprises a derived unit from a compound represented by Formula 1, and a functional group derived from a modifier represented by Formula 2 at the other terminal: Wherein in Formula 1, R 1 is a hydrogen atom or a monovalent hydrocarbon group of 1 to 20 carbon atoms, R 2 is a divalent hydrocarbon group of 1 to 20 carbon atoms, which is unsubstituted or substituted with one or more substituents selected from the group consisting of an alkyl group of 1 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, and an aryl group of 6 to 30 carbon atoms, R 3 and R 4 are each independently a monovalent hydrocarbon group of 1 to 20 carbon atoms, which is unsubstituted or substituted with one or more substituents selected from the group consisting of an alkyl group of 1 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, and an aryl group of 6 to 30 carbon atoms, and X is S or O, wherein in Formula 2, R 5 and R 6 are each independently a monovalent hydrocarbon group of 1 to 30 carbon atoms or a glycol unit represented by wherein at least one of R 5 and R 6 is the glycol unit, R 7 is a single bond or a divalent hydrocarbon group of 1 to 30 carbon atoms, R 8 to R 11 are each independently a monovalent hydrocarbon group of 1 to 30 carbon atoms, R 12 is a divalent hydrocarbon group of 1 to 10 carbon atoms, j and k are each independently 0 or 1, and n is an integer of 1 to 10, wherein if R 5 is the glycol unit, 3-i-l and i are each independently 1 or 2 but are not 2 at the same time, and l is 0 or 1, if R 6 is the glycol unit, i and 1 are each independently 1 or 2 but are not 2 at the same time, and 3-i-1 is 0 or 1, and if both R 5 and R 6 are the glycol units, i is 1 or 2, and l and 3-i-l are each independently 0 or 1 but are not 0 at the same time. R 1 is a hydrogen atom or a monovalent hydrocarbon group of 1 to 20 carbon atoms, R 2 is a divalent hydrocarbon group of 1 to 20 carbon atoms, which is unsubstituted or substituted with one or more substituents selected from the group consisting of an alkyl group of 1 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, and an aryl group of 6 to 30 carbon atoms, R 3 and R 4 are each independently a monovalent hydrocarbon group of 1 to 20 carbon atoms, which is unsubstituted or substituted with one or more substituents selected from the group consisting of an alkyl group of 1 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, and an aryl group of 6 to 30 carbon atoms, and X is S or O, R 5 and R 6 are each independently a monovalent hydrocarbon group of 1 to 30 carbon atoms or a glycol unit represented by wherein at least one of R 5 and R 6 is the glycol unit, R 7 is a single bond or a divalent hydrocarbon group of 1 to 30 carbon atoms, R 8 to R 11 are each independently a monovalent hydrocarbon group of 1 to 30 carbon atoms, R 12 is a divalent hydrocarbon group of 1 to 10 carbon atoms, j and k are each independently 0 or 1, and n is an integer of 1 to 10, wherein if R 5 is the glycol unit, 3-i-l and i are each independently 1 or 2 but are not 2 at the same time, and l is 0 or 1, if R 6 is the glycol unit, i and 1 are each independently 1 or 2 but are not 2 at the same time, and 3-i-1 is 0 or 1, and if both R 5 and R 6 are the glycol units, i is 1 or 2, and l and 3-i-l are each independently 0 or 1 but are not 0 at the same time.