Provided is a positive electrode active material that can be used to fabricate a nonaqueous electrolyte secondary battery having excellent output characteristics not only in an environment at normal temperature but also in all temperature environments from extremely low to high temperatures.A positive electrode active material for nonaqueous electrolyte secondary batteries, the positive electrode active material includes a boron compound and lithium-nickel-cobalt-manganese composite oxide of general formula (1) having a layered hexagonal crystal structure. The lithium-nickel-cobalt-manganese composite oxide includes secondary particles composed of agglomerated primary particles. The boron compound is present on at least part of the surface of the primary particles, and contains lithium. Li1+sNixCoyMnzMotMwO2  (1)