Provided is a cathode active material including lithium transition metal oxide particles and composite particles, wherein the composite particles include any one selected from the group consisting of yttria stabilized zirconia (YSZ), gadolinia-doped ceria (GDC), lanthanum strontium gallate magnesite (LSGM), lanthanum strontium manganite (LSM), and nickel (Ni)—YSZ, or a mixture of two or more thereof, and the cathode active material includes the composite particles having a single-phase peak when analyzed by X-ray diffraction (XRD). A cathode active material according to an embodiment of the present invention may not only minimize the reduction in capacity or output of a secondary battery, but may also further improve life characteristics.