Negative electrode active material, method of preparing the same and lithium secondary battery including negative electrode active material

A negative electrode active material, a method of preparing the negative electrode active material and a lithium secondary battery including the negative electrode active material. A negative electrode active material includes a lithium titanate, wherein a portion of lithium of the lithium titanate is substituted by at least one selected from the group consisting of Sr, Ba, a mixture thereof and an alloy thereof, and thus a lithium secondary battery including the negative electrode active material may improve high-rate discharge characteristics.