A method for pre-lithiation and pre-sodiation of a negative electrode, including the steps of: interposing a first separator between a lithium ion-supplying metal sheet and a negative electrode to prepare a first simple cell. Then, dipping the first simple cell in an electrolyte for pre-lithiation. Next, carrying out a primary electrochemical charging of the first simple cell dipped in the electrolyte for pre-lithiation to obtain a pre-lithiated negative electrode. Then, interposing a second separator between a sodium ion-supplying metal sheet and the pre-lithiated negative electrode to prepare to prepare a second simple cell. Next, dipping the second simple cell in an electrolyte for pre-sodiation; and carrying out secondary electrochemical charging of the second simple cell dipped in the electrolyte for pre-sodiation to obtain a pre-lithiated and pre-sodiated negative electrode. A pre-lithiated/pre-sodiated negative electrode obtained by the method and a lithium secondary battery including the same are also disclosed.