Provided are a method of manufacturing a lithium nickel complex oxide including mixing a nickel-containing mixed transition metal precursor, a lithium compound, and a polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer, and heat treating the mixture, a lithium nickel complex oxide manufactured thereby, and a cathode active material including the lithium nickel complex oxide. The method of manufacturing a lithium nickel complex oxide according to an embodiment of the present invention may adjust a ratio of divalent nickel (NiII) to trivalent nickel (NiIII) by using a polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer, and thus, the method may improve capacity of a secondary battery.