A method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery, the method includes preparing nickel-containing composite oxide particles having a ratio 1D90/1D10 of a 90% particle size 1D90 to a 10% particle size 1D10 in volume-based cumulative particle size distribution of 3 or less; obtaining a raw material mixture containing the composite oxide particles and a lithium compound and having a ratio of a total number of moles of lithium to a total number of moles of metal elements contained in the composite oxide in a range of 1 to 1.3; subjecting the raw material mixture to a heat treatment to obtain a heat-treated material; subjecting the heat-treated material to a dry-dispersion treatment to obtain a first dispersion; and bringing the first dispersion into contact with a liquid medium to obtain a second dispersion.