A cathode active material including at least two agglomerates of primary particles and a cathode and a lithium secondary battery containing the same are disclosed. In the cathode active material, a secondary particle includes a nickel-based lithium transition metal oxide, an average particle diameter of each primary particle is in a range from about 2 to about 3 μm, and an average particle diameter of the secondary particle is in a range from about 5 to about 8 μm.