A modified conjugated diene-based polymer comprising: a first chain comprising a repeating unit derived from a conjugated diene-based monomer; a second chain comprising a repeating unit derived from a compound represented by the following Formula 1; and a derived unit from an alkoxysilane-based modifier, wherein the first chain and the second chain are coupled by the derived unit from the modifier: in Formula 1, R 11a and R 11b are each independently a single bond or a substituted with a substituent or unsubstituted alkylene group of 1 to 20 carbon atoms; a substituted with a substituent or unsubstituted cycloalkylene group of 5 to 20 carbon atoms; or a substituted with a substituent or unsubstituted arylene group of 6 to 20 carbon atoms, wherein the substituent is an alkyl group of 1 to 10 carbon atoms, a cycloalkyl group of 5 to 10 carbon atoms, or an aryl group of 6 to 20 carbon atoms, R 11c is an alkyl group of 1 to 20 carbon atoms; an alkynyl group of 2 to 20 carbon atoms; a heteroalkyl group of 1 to 20 carbon atoms; a heteroalkenyl group of 2 to 20 carbon atoms; a heteroalkynyl group of 2 to 20 carbon atoms; a cycloalkyl group of 5 to 20 carbon atoms; an aryl group of 6 to 20 carbon atoms; or a heterocyclic group of 3 to 20 carbon atoms, and R 11d to R 11g are each independently an alkyl group of 1 to 20 carbon atoms; an alkenyl group of 2 to 20 carbon atoms; an alkynyl group of 2 to 20 carbon atoms; a heteroalkyl group of 1 to 20 carbon atoms; a heteroalkenyl group of 2 to 20 carbon atoms; a heteroalkynyl group of 2 to 20 carbon atoms; a cycloalkyl group of 5 to 20 carbon atoms; an aryl group of 6 to 20 carbon atoms; a heterocyclic group of 3 to 20 carbon atoms; or a mono-substituted, di-substituted or tri-substituted alkylsilyl group with alkyl groups of 1 to 10 carbon atoms. a first chain comprising a repeating unit derived from a conjugated diene-based monomer; a second chain comprising a repeating unit derived from a compound represented by the following Formula 1; and a derived unit from an alkoxysilane-based modifier, wherein the first chain and the second chain are coupled by the derived unit from the modifier: in Formula 1, R 11a and R 11b are each independently a single bond or a substituted with a substituent or unsubstituted alkylene group of 1 to 20 carbon atoms; a substituted with a substituent or unsubstituted cycloalkylene group of 5 to 20 carbon atoms; or a substituted with a substituent or unsubstituted arylene group of 6 to 20 carbon atoms, wherein the substituent is an alkyl group of 1 to 10 carbon atoms, a cycloalkyl group of 5 to 10 carbon atoms, or an aryl group of 6 to 20 carbon atoms, R 11c is an alkyl group of 1 to 20 carbon atoms; an alkynyl group of 2 to 20 carbon atoms; a heteroalkyl group of 1 to 20 carbon atoms; a heteroalkenyl group of 2 to 20 carbon atoms; a heteroalkynyl group of 2 to 20 carbon atoms; a cycloalkyl group of 5 to 20 carbon atoms; an aryl group of 6 to 20 carbon atoms; or a heterocyclic group of 3 to 20 carbon atoms, and R 11d to R 11g are each independently an alkyl group of 1 to 20 carbon atoms; an alkenyl group of 2 to 20 carbon atoms; an alkynyl group of 2 to 20 carbon atoms; a heteroalkyl group of 1 to 20 carbon atoms; a heteroalkenyl group of 2 to 20 carbon atoms; a heteroalkynyl group of 2 to 20 carbon atoms; a cycloalkyl group of 5 to 20 carbon atoms; an aryl group of 6 to 20 carbon atoms; a heterocyclic group of 3 to 20 carbon atoms; or a mono-substituted, di-substituted or tri-substituted alkylsilyl group with alkyl groups of 1 to 10 carbon atoms. R 11a and R 11b are each independently a single bond or a substituted with a substituent or unsubstituted alkylene group of 1 to 20 carbon atoms; a substituted with a substituent or unsubstituted cycloalkylene group of 5 to 20 carbon atoms; or a substituted with a substituent or unsubstituted arylene group of 6 to 20 carbon atoms, wherein the substituent is an alkyl group of 1 to 10 carbon atoms, a cycloalkyl group of 5 to 10 carbon atoms, or an aryl group of 6 to 20 carbon atoms, R 11c is an alkyl group of 1 to 20 carbon atoms; an alkynyl group of 2 to 20 carbon atoms; a heteroalkyl group of 1 to 20 carbon atoms; a heteroalkenyl group of 2 to 20 carbon atoms; a heteroalkynyl group of 2 to 20 carbon atoms; a cycloalkyl group of 5 to 20 carbon atoms; an aryl group of 6 to 20 carbon atoms; or a heterocyclic group of 3 to 20 carbon atoms, and R 11d to R 11g are each independently an alkyl group of 1 to 20 carbon atoms; an alkenyl group of 2 to 20 carbon atoms; an alkynyl group of 2 to 20 carbon atoms; a heteroalkyl group of 1 to 20 carbon atoms; a heteroalkenyl group of 2 to 20 carbon atoms; a heteroalkynyl group of 2 to 20 carbon atoms; a cycloalkyl group of 5 to 20 carbon atoms; an aryl group of 6 to 20 carbon atoms; a heterocyclic group of 3 to 20 carbon atoms; or a mono-substituted, di-substituted or tri-substituted alkylsilyl group with alkyl groups of 1 to 10 carbon atoms.