Disclosed are a negative active material for a rechargeable lithium battery that includes a core including silicon oxide represented by the following Chemical Formula 1; and a surface-treatment layer surrounding the core and including metal oxide represented by the following Chemical Formula 2, a method of preparing the negative active material, and a rechargeable lithium battery including the negative active material. The metal of the metal oxide is included in an amount of about 0.1 wt % to about 20 wt % based on the total weight of the negative active material for a rechargeable lithium battery. SiOx  [Chemical Formula 1] MyOz  [Chemical Formula 2] In the above Chemical Formula 1 and 2, M, x, y, and z are the same as defined in the specification.