The 75-year-old Dikshit was administered the oath by Kerala High Court Chief Justice Dr Manjula Chellur.
Dikshit was appointed Governor of Kerala on March 04, within three months of her defeat in the recent Delhi Assembly polls. She was appointed to the post following the resignation of Nikhil Kumar, a former Delhi Police chief.
Dikshit served as Delhi's chief minister from 1998 to 2013 before the Congress was crushed in the 2013 Assembly polls, only securing eight seats in the 70-member Assembly.
She herself lost to Aam Aadmi Party leader Arvind Kejriwal by over 20,000 votes. She has also represented the Kannauj Parliamentary constituency in Uttar Pradesh between 1984 and 1989.
Kejriwal, who succeeded Dikshit as chief minister, has since resigned over the Jan Lokpal Bill issue.
With PTI inputs