Kerala High Court Chief Justice Manjula Chellur administered the oath of office. Chief Minister Oommen Chandy and his cabinet colleagues were also present on the occasion.
75-year0old Dikshit succeeds Nikhil Kumar, who resigned as the state's Governor to contest in upcoming Lok Sabha polls from Aurangabad seat in Bihar.
A group of well-wishers of Dikshit, including her family members and former cabinet colleagues, were present at the occasion.
Dikshit served as Chief Minister of Delhi from 1998 to 2013 before Congress was defeated in the 2013 assembly polls.