This positive electrode active material for nonaqueous electrolyte secondary batteries includes a Ni-containing lithium composite oxide A and Ni-containing lithium composite oxide B. The Ni-containing lithium composite oxide A contains at least 55 mol % of Ni relative to the total number of mols of metal elements other than Li. The Ni-containing lithium composite oxide B contains Ti and Ni. The Ni content in the Ni-containing lithium composite oxide B is at least 55 mol % relative to the total number of mols of metal elements other than Ti and Li. The Ni-containing lithium composite oxide A and the Ni-containing lithium composite oxide B have a prescribed average first particle diameter and a prescribed average second particle diameter, respectively, and the ratio between the Ni-containing lithium composite oxide A and the Ni-containing lithium composite oxide B is, in mass ratio, 5:95-55:45.