The present invention provides a positive electrode active material for a secondary battery and a secondary battery including the same, which includes a core; a shell located to surround the core; and a buffer layer located between the core and the shell, and including a three-dimensional network structure connecting the core and the shell and a pore. The decomposition of the active material may be minimized by a rolling process in the manufacture of an electrode by controlling the specific surface area, average particle diameter and porosity of the active material particles as well as the specific structure, the reactivity with an electrolyte solution may be maximized, and the output and lifespan characteristics of the secondary battery may be improved since the particles forming the shell have crystal structure with orientation which facilitates intercalation and deintercalation of lithium ions.