A positive electrode active material for a non-aqueous electrolyte secondary battery according to a configuration includes a lithium-transition metal composite oxide containing nickel (Ni) in an amount of greater than or equal to 80 mol %, in which boron (B) is present at least on a particle surface of the lithium-transition metal composite oxide. In the lithium-transition metal composite oxide, when particles having a larger particle size than a volume-based 70% particle size (D70) are first particles and particles having a smaller particle size than a volume-based 30% particle size (D30) are second particles, a coverage ratio of B on surfaces of the first particles is larger than a coverage ratio of B on surfaces of the second particles by 5% or greater.