Her mother was the Grand Minister and a seii taishogun (literally, "great general who subdues the barbarians") Hidetada TOKUGAWA's daughter, Tofukumon-in Kazuko TOKUGAWA. (When she entered the Imperial Palace, her name, Kazuko was changed to Masako as her original name was not a preferred one under Palace customs.)
母は太政大臣征夷大将軍徳川秀忠の娘、東福門院徳川和子（かずこ、入内の際に濁音発音を嫌う宮廷風習にならい「まさこ」と読みを変える）。