The present disclosure relates to a nanocomposite cathode active material for a lithium secondary battery, a method for preparing same, and a lithium secondary battery including same. More particularly, the present disclosure relates to a nanocomposite cathode active material for a lithium secondary battery including: a core including LiMn2O4; and LiMn(PO3)3 distributed on the surface of the core. In accordance with the present disclosure, the time and cost for manufacturing a lithium secondary battery can be reduced and the manufactured lithium secondary battery has superior electrochemical properties.