Initially she was just one of Emperor SAGA's Empress but after Imperial Princess Takatsu, Emperor Kanmu's Princess, deposed from the Empress, her relative in law, FUJIWARA no Fuyutsugu (Kachiko's older sister, Yasuko was FUJIWARA no Mimori's wife, who was the younger brother of Fuyutsugu's wife, FUJIWARA no Mitsuko) supported Kachiko to become Empress.
もとは嵯峨天皇の数多い夫人の一人に過ぎなかったが、桓武天皇皇女の高津内親王が后を廃された後、姻戚である藤原冬嗣（嘉智子の姉安子は冬嗣夫人藤原美都子の弟藤原三守の妻だった）らの後押しで立后した。