A composite cathode active material includes: a first metal oxide including a plurality of layered crystalline phases comprising a first layered crystalline phase and a second layered crystalline phase, wherein the first and second layered crystalline phases have a different compositions than each other, and a second metal oxide different from the first metal oxide and including a composite crystalline phase, that is different from the first metal oxide, wherein the second metal oxide is represented by Formula 1, wherein at least a portion of the second metal oxide is disposed on a first layered crystalline phase of the plurality of layered crystalline phases of the first metal oxide, and wherein the first layer crystalline phase is in a space group of R-3m: LixMyOz  Formula 1 wherein, in Formula 1, 0≤x≤3, 1≤y≤3, and 2≤z≤8, and M is at least one selected from a Group 4 element to a Group 13 element.