The order appointing Sahai, a 1986 batch Union Territory cadre officer, was issued by Union Home Ministry, official sources said.
Sahai's name was zeroed in as a compromise candidate for the high post after continuous tussle between the LG and the Arvind Kejriwal-led government.
So far, there were two Home Secretaries in Delhi -- one appointed by the AAP government and the other continues to hold the office despite a removal order by the city government.
Kumar has been functioning as Home Secretary despite clear directive by the Union Home Ministry that Pal should be allowed to work without any hindrance.
Pal was removed by the AAP government after he signed a notification appointing Joint Commissioner of Delhi Police M K Meena as new chief of Anti-Corruption Branch (ACB) following Jung's order.
Jung on June 8 had appointed Meena superseding Kejriwal's hand-picked chief S S Yadav. The AAP government had challenged the appointment in Delhi High Court.