Disclosed is a modified conjugated diene polymer wherein a modifying group derived from a low molecular weight compound having two or more tertiary amino groups and one or more alkoxysilyl groups in a molecule is bonded to a conjugated diene polymer obtained by polymerizing a conjugated diene compound or to a conjugated diene polymer obtained by copolymerizing a conjugated diene compound and an aromatic vinyl compound. Also disclosed is a method for producing the modified conjugated diene polymer which is characterized in that after polymerizing a conjugated diene compound or copolymerizing aconjugated diene compound and an aromatic vinyl compound in a hydrocarbon solvent using an alkali metal initiator and/or an alkaline earth metal initiator, an active end of the thus-obtained polymer is reacted with a low molecular weight compound having two or more tertiary amino groups and one or more alkoxysilyl groups in a molecule.