The positive electrode active material is for a non-aqueous electrolyte secondary battery, suppressing deterioration of battery characteristics due to exposure to the atmosphere and having excellent battery capacity. A positive electrode active material for a non-aqueous electrolyte secondary battery includes a lithium-nickel composite oxide represented by general formula (1): LiaNi1−x−yCoxMyO2+α (in which 0.05≤x≤0.35, 0≤y≤0.10, 0.95≤a≤1.10, 0≤a≤0.2, and M represents at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W, and Al) and Li3BO3. At least a part of a surface of the lithium-nickel composite oxide is coated with Li3BO3. The content of boron in the positive electrode active material is 0.001% by mass or more and 0.2% by mass or less with respect to the entire positive electrode active material.