A positive active material, a method of preparing the positive active material, a positive electrode including the positive active material, and a lithium battery including the positive active material are disclosed. The positive active material includes a core and a coating layer on the core. The coating layer includes a sulfur component. When a binding energy peak of the sulfur is measured by X-ray photoelectron spectroscopy (XPS), the binding energy peak is observed at about 165 eV to about 168 eV, and the stability of the positive active material may be improved due to the coating layer. Accordingly, the lifespan properties of a lithium battery including the positive active material may be improved.