A method of preparing a positive electrode active material precursor, the method comprising: a first step of preparing a transition metal aqueous solution including a nickel raw material, a cobalt raw material, and a manganese raw material; a second step of preparing a reaction mother liquor by adding an ammonium cationic complexing agent, a basic compound, and water to a reactor, wherein a pH of the reaction mother liquor in the second step is in a range of 11.7 to 11.9; a third step of forming a reaction solution by adding the transition metal aqueous solution, an ammonium cationic complexing agent, and a basic compound to the reactor, in which the reaction mother liquor has been accommodated, and co-precipitating the reaction solution to form a core of a positive electrode active material precursor particle; a fourth step of adjusting a pH of the reaction solution to be higher than a pH of the reaction solution of the third step to grow the positive electrode active material precursor particle; and a fifth step of stabilizing the positive electrode active material precursor particle, wherein an average particle diameter growth rate of the positive electrode active material precursor particle in the fifth step is 0.10 μm/hr or less, wherein, in the fifth step, the stabilizing is performed for 10% or more of a sum of reaction times of the third step and the fourth step; wherein the positive electrode active material precursor is a nickel-cobalt-manganese hydroxide, a nickel-cobalt-manganese oxyhydroxide, or a mixture thereof, and a molar ratio of nickel in total transition metals in the hydroxide or oxyhydroxide is 60 mol% or more; wherein the nickel raw material is Ni 2, NiO, NiOOH, NiCO 3 ·2Ni 2 ·4H 2 O, NiC 2 O 2 ·2H 2 O, Ni (NO 3) 2 ·6H 2 O, NiSO 4, NiSO 4 ·6H 2 O, a fatty acid nickel salt, or a nickel halide, and any one thereof or a mixture of two or more thereof; wherein the cobalt raw material is Co 2, CoSO 4, CoOOH, Co(OCOCH 3) 2 ·4H 2 O, Co(NO 3) 2 ·6H 2 O, or CoSO 4 ·7H 2 O, and any one thereof or a mixture of two or more thereof; wherein the manganese raw material is a manganese oxide such as Mn 2 O 3, MnO 2, and Mn 3 O 4; a manganese salt such as MnCO 3, Mn(NO 3) 2, MnSO 4, manganese acetate, manganese dicarboxylate, manganese citrate, and a fatty acid manganese salt; an oxyhydroxide, and manganese chloride, and any one thereof or a mixture of two or more thereof; and wherein the transition metal aqueous solution includes the nickel raw material such that an amount of nickel is 60 mol% or more based on a total number of moles of transition metals. a first step of preparing a transition metal aqueous solution including a nickel raw material, a cobalt raw material, and a manganese raw material; a second step of preparing a reaction mother liquor by adding an ammonium cationic complexing agent, a basic compound, and water to a reactor, wherein a pH of the reaction mother liquor in the second step is in a range of 11.7 to 11.9; a third step of forming a reaction solution by adding the transition metal aqueous solution, an ammonium cationic complexing agent, and a basic compound to the reactor, in which the reaction mother liquor has been accommodated, and co-precipitating the reaction solution to form a core of a positive electrode active material precursor particle; a fourth step of adjusting a pH of the reaction solution to be higher than a pH of the reaction solution of the third step to grow the positive electrode active material precursor particle; and a fifth step of stabilizing the positive electrode active material precursor particle, wherein an average particle diameter growth rate of the positive electrode active material precursor particle in the fifth step is 0.10 μm/hr or less, wherein, in the fifth step, the stabilizing is performed for 10% or more of a sum of reaction times of the third step and the fourth step; wherein the positive electrode active material precursor is a nickel-cobalt-manganese hydroxide, a nickel-cobalt-manganese oxyhydroxide, or a mixture thereof, and a molar ratio of nickel in total transition metals in the hydroxide or oxyhydroxide is 60 mol% or more; wherein the nickel raw material is Ni 2, NiO, NiOOH, NiCO 3 ·2Ni 2 ·4H 2 O, NiC 2 O 2 ·2H 2 O, Ni (NO 3) 2 ·6H 2 O, NiSO 4, NiSO 4 ·6H 2 O, a fatty acid nickel salt, or a nickel halide, and any one thereof or a mixture of two or more thereof; wherein the cobalt raw material is Co 2, CoSO 4, CoOOH, Co(OCOCH 3) 2 ·4H 2 O, Co(NO 3) 2 ·6H 2 O, or CoSO 4 ·7H 2 O, and any one thereof or a mixture of two or more thereof; wherein the manganese raw material is a manganese oxide such as Mn 2 O 3, MnO 2, and Mn 3 O 4; a manganese salt such as MnCO 3, Mn(NO 3) 2, MnSO 4, manganese acetate, manganese dicarboxylate, manganese citrate, and a fatty acid manganese salt; an oxyhydroxide, and manganese chloride, and any one thereof or a mixture of two or more thereof; and wherein the transition metal aqueous solution includes the nickel raw material such that an amount of nickel is 60 mol% or more based on a total number of moles of transition metals.